Area: WHALER Forum: ContinuousWave: Whaler Repairs/Mods
Topic: Mercury Oil Injection System

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jimh posted 03-19-2006 10:22 AM ET (US)
Use this thread for any questions or comments on the Mercury Oil Injection System as described in the REFERENCE section article,

Mercury Oil Injection System

migalito posted 04-04-2006 09:24 AM ET (US)
I recently purchase a center console with a 200 efi merc. I noticed that there was not a horn on the boat and the wire to the horn had been cut. I installed a horn and took the boat for a spin. After 5 minutes of run time the horn began to beep constantly, beep, beep, beep- not continously. It never stopped. Any ideas what this means?
Tom W Clark posted 04-04-2006 10:32 AM ET (US)
That is the No Oil warning. It should not be ignored.

It is entirely possible that the alarm module itself has become defective and is sounding the alarm even though the motor is getting oil, but you need to deduce if this is the case before using the motor again.

The faulty alarm module is a common problem among the Mercury motors. I have suffered through his problem myself as have many others here.

Then there are those who will simply cut the wire to the horn to solve his particular problem. My outboard mechanic says he has rebuilt many outboards where the wire to the horn has been cut.

On the other hand if the alarm does not sound until the boat has been run for five minutes, you may have a genuine oil starvation problem.

migalito posted 04-04-2006 02:16 PM ET (US)
Thanks Tom for the info. I checked the remote and the oil reseroir on the motor and both have plenty of oil. Is there a way to verify that it is the module? Are they expensive?
Tom W Clark posted 04-04-2006 02:22 PM ET (US)
There are test procedures described in the article above.

You must run the motor on a tank of premixed gas while doing this testing. You should assume the motor is not getting oil until you can confirm that it is.

The alarm module costs about $200 if I remember correctly. Also read:

rsess1 posted 04-04-2006 02:27 PM ET (US)
I had to replace the oil alarm on my 1994 Mercury 175 EFI this past June, when the exact same thing happened with constant alarm. I did add oil to the fuel tank just in case and monitored water temp that weekend. Replaced module for about $200. Good to go.
migalito posted 04-04-2006 02:34 PM ET (US)
Thanks once again Tom! I will do some testing this evening and see what I can come up with....
migalito posted 04-05-2006 09:07 AM ET (US)
Hi Tom,
I did some testing last night, not a lot it got dark before I was able to do much. I filled a very large livestock water trough, about 100 gallons, with water and lowered the drive into the water. Started the engine and let it idle. Within 1 minute the alarm started beeping. The engine was producing a lot of blue smoke so I assume it is oiling. I checked the float in the engine reservoir and it was moving freely. Hopefully tonight I will be able to do more testing.
However, being a retired auto technician I noticed the engine seemed to be rattling internally alot, not really knocking like an auto engie when it has worn bearings. More like what we called gear rollover. A codition that is noticable on manual transmisions which is really just the gears rattling together at idle. Not an uncommon noise. Is this something I should be concerned about? Guess with the engine cove off it was more noticable.
jimh posted 04-05-2006 09:25 AM ET (US)
Tom--I did not realize your Mercury oil injection system alarm electronic module had failed. That makes it three for three of the owners I know with that problem.

Unfortunately the module just sounds the same alarm no matter what part of the oil system is signalling. If the alarm is a steady BEEP, it is an over heat alarm. If the alarm is a BEEP BEEP BEEP, it is an oil alarm, and is caused by either:

--oil level float switch in reservoir

--magnetic sensor in oil mixing pump input drive shaft has stopped rotation

--a defect in the alarm module itself (apparently a common failure)

Because there are no indicators and the cadence of the alarm tone is the same, you have to deduce which sensor is causing the problem.

You can deduce if the problem is the oil level in the under-cowling reservoir by checking the level. If the level is at its normal condition, almost full, the float switch could be signaling a false alarm. You can check this with a meter to see if the switch is actually signaling an alarm.

If is much more difficult to assess the motion sensor. Monitor the output of the motion sensor alarm and verify that it produces an output pulse of 5-volts for every two rotations of the engine crankcase.

If the motion sensor checks out, the next step is to change the engine's fuel supply to a pre-mix 1:50 oil:gas ratio source, and run the engine. You then disassemble the oil pump output hose and check to see if it is actually pumping oil.

If, after all of these checks, the alarm condition persists, you conclude the alarm module itself is defective and replace the alarm module.

jimh posted 04-05-2006 09:32 AM ET (US)
Oops--forgot to mention this additional check:

--Check the voltages being supplied to the alarm modules, including the pulses from the ignition module. It could be the problem is not in the alarm module at all, but is caused by a failure of the the ignition module to provide the proper voltage pulse.

I will try to expand the REFERENCE article to include more detail on troubleshooting the alarm module for the Mercury system.

I would guess that a lot of experienced Mercury mechanics may try a new alarm module in lieu of making all the checks suggested above. The labor for all that testing is probably as much as a new module, so a customer is going to pay as much to test the module as it costs to replace it. If the module has a history of failure, they may try to save the customer the time and money of testing it first.

migalito posted 04-05-2006 02:02 PM ET (US)
Thanks for all the great info Jim! I will be performing these test myself in hopes of saving money.
jimh posted 04-06-2006 11:49 PM ET (US)
Because of the high cost of repair of a failure of the plastic drive gear in the Mercury oil injection system, an alternative after-market solution has been developed. It replaces the OEM oil mixing pump with an electrically operated pump.

The cost of a gear replacement is estimated at $1,200. The cost of retrofitting an electrically operated pump is estimated at $575.

For more information on this solution, see:

Marine Solutions (Wisconsin)

They have retrofit kits available for Mercury V6 outboards:

--135 to 200-HP, 1989 through 1999

--200 to 225-HP, 1995 through 2001 3-liter

The manufacturer of this retrofit comes with some credentials. Robert Kachelek, president of Marine Solutions, was formerly the director of Outboard Service for Mercury Marine.

rexford posted 05-08-2006 01:18 PM ET (US)
Dear ContinuousWave

I was directed to you in hopes that you could
offer your experience in a problem with my
Merc 150 V6. I am sure you are aware of the
nylon or plastic oil pump gear problems. I
am in the middle of my third and have decided
to bypass the pump all together. My only
fear in doing this is leaving any plastic shavings
in the crankcase by not cracking the powerhead
to remove the failed gear. If anyone would
be an expert in this situation it would be
you folks. If I could burden you for your
opinion I would be grateful.

Would leaving these very small plastic shavings
pose a huge risk? Is there a way to remove the
shavings without pulling the powerhead?

Thank you very much for your time and thank
you very much for your help.


jeffs22outrage posted 06-26-2006 02:27 PM ET (US)

I wanted to say thanks for this article. My father spent a day and a half trying to diagnosis why the warning horn was bleeping on one of his Merc 150's. After swapping all of the sensors from one motor to the other, redoing all the grounds, and many other things he had enough. This was one of the FEW times I have seen him admit his just could not figure it out. After closing up shop because of rain, I went to the trusty reference section here and with in 5 minutes we were able to tell what was wrong.

My father contacted the gentleman from on Monday and ordered the kit. It arrived (Detroit area) either Tuesday or Wednesday. The price was under $500.oo which was much cheaper than the $1400.oo quoted to replace the OEM pump.

He installed the kit and unfortunatly still had the warning horn. After a couple phone calls to they were able to finally figure out it was a faulty wire on the oil float. Probably the problem from the beginning but, oh well. At least we know the oil pump is now good to go.

SO A++, on the customer service from

I will ask him to post about the installation..


flycast47 posted 06-29-2006 10:44 AM ET (US)
I have been working with a 1986 Merc 175 with an oil warning system problem condition and wanted to add some information regarding the failure diagnosis process. The oil tank float sensor can be checked using a volt-ohm meter. The float creates a closed circuit when the tank level drops. Connecting the VOM to the float sensor leads should show no resistance [continuity] when the float lowered on its shaft, and inifinite resistance (open circuit) at the top of the shaft.

As mentioned elsewhere, the oil pump motion sensor should produce a 5-volt pulse every two revolutions. In order to do this [the oil pump motion sensor] must be getting 12-volt input from the white wire connecting it to the warning module when the ignition is on. You must verify that the 12-volt source is present before checking for the 5-volt pulse. If it is not, then the warning module is probably defective. If some voltage is available when checking the white wire (the negative lead of the vom is connected to a ground on the motor) you may still verify the presence of a pump sensor pulse though it will not be a 5-volt pulse. To produce the pulse the engine must be rotated with the emergency starter rope and the flywheel. with the sparkplugs removed.

I hope that this is information is useful.

gbrannon posted 07-23-2006 01:29 PM ET (US)
I have a mercury 200 HP 2.5 L outboard 1995 off shore The alarm went of the temp was high I think grass at idle speed caused it. I was not on the boat at the time. I got on the boat and ran it. It cooled down but alarm stayed on I took it home and let it cool down. The alarm comes on when cranked it is a steady alarm don't know if it is the oil alarm or false temp. justed replaced sensor oil cap a while back I checked all conections they looked fine have put many hours on motor since I replaced the oil cap. any help Thanks
Dos Guidos posted 07-28-2006 06:46 PM ET (US)
I experienced an oil injection system alarm last weekend and avoided engine damage but would like some input as to what caused the alarm. The problem was a cracked cap on the 1 liter (engine mounted) oil reservoir. The crack allowed the remote reservoir to pump 2.5 gallons of oil out through the broken cap into the lower areas of the engine compartment (what a mess). The 1 liter oil reservoir was full when checked.
To get back underway, I transfered a gallon of oil from the other remote reservoir (twin OB)into the empty one and started the motor, and the alarm did not sound. I assumed the remote tank had an alarm and sounded when emptied. After reading articles on this site, there is no alarm in the remote tank. Only thing I can conclude is that the low oil float sensor in the 1 liter reservoir barely engaged during all the oil pumping throught the crack. I replaced BOTH caps at $42 each. These are 1990 135 Black Max with 700 hours on a (sorry to all BW fans) 24 SeaRay Laguna FDC. Prior owner had wires all twisted around and insulation was missing on the cracked one.
Thought I would share this as all warning systems worked as designed. Comments anyone (besides my choise in boat brands?
barefoot200 posted 08-01-2006 10:20 AM ET (US)
Same as some of the other people, the BEEP BEEP BEEP BEEP at two-minute intervals started on my 2002 Mercury EFI 200-HP, 153 cubic inches. We were on vaction, so our regular technician was not an option. [Someone] checked out the engine with an ohm meter, and according to the manual he showed me, he decided that the the sensor in the engine-mounted reservoir was faulty. As a temporary fix, he bypassed the the sensor by attaching a piece of wire in the circuit where the reservoir would normally be. He said that this would stop the beeping. The beeping DID stop for a while, but then started again. Did the circuit bypass damage something else? I ordered a new engine mounted reservoir. Any tips on installation?
bsmotril posted 08-01-2006 11:52 AM ET (US)
The cracked cap for the under cowl resevoir is probably the most common failure point for the Merc Oil System across the mid to highpower 2 stroke and DFI product line. Join the club, a lot of us have also already been there too. BillS
jimh posted 08-01-2006 08:11 PM ET (US)
barefoot200--I have deleted the duplicate article you posted with this same inquiry. Please don't post duplicate articles.

Perhaps the temporary jumper in the oil reservoir float switch circuit came loose. It is hard to predict what happened. I don't see how the temporary jumper could have caused a problem. As far as the alarm module can tell, a closed circuit is a closed circuit, and it doesn't know if it is a float switch or a jumper. The alarm modules on these engines seem to have a history of problems. Perhaps the alarm module is acting up now, too.

Installing the new reservoir float switch should not be too difficult. Let us know how it goes. Also, what is that part number? It might be handy to have if it is a common problem and often replaced.

barefoot200 posted 08-07-2006 12:35 PM ET (US)
Thank you for your response. Since I wrote last, the new (engine-mounted) reservior arrived. I installed it, and ran it for 10 minutes in a test tank. No beeping. From what I have read here at continuous wave, it sounds like the alarm modules are the more common problem. If the beeping starts again, I'll order one and replace it. I'll have a chance to use the boat in two days.

Sorry about the duplicate message. The first time I posted my question, I clicked new message instead of post reply.

crbenny posted 08-17-2006 02:39 PM ET (US)
I had the alarm module fail on my '87 135 Black Max last year. I also had a switch box failing intermittently and this can cause the alarm as well I'm told because the module's power source is whichever switchbox it's wired to. As far as the plastic gear goes, I spoke with Peter Nopper of Nopper Marine in Fairhaven, Ma. and he told me those plastic gears have a tendency to fail if the engine's been overheated so, you guys that run them hard or anyone thats lost an impeller, you may want to check it. One other word of advice he gave me was ign. timing. You guys may remember my post 2 weeks ago when I thought my initial timing was retarded. I advanced it one turn and sure enough it ran great, however my top speed was still down. I surmised that the total timing was most likely retarded as well. I shared this with Peter and he suggested that I should live with the 300 rpm loss and not get too agressive with the timing. Evidently, since the 10% ethinol in marine fuel in Ma. he's had a few customers melt their powerheads.
Benn posted 08-21-2006 04:14 PM ET (US)
Great information on this thread. Thanks to all.

Hoping for a some help trouble shooting my own oil alarm [problem]. I have a 1995 75 HP Merc that is giving me the oil alarm right when I turn the ignition key from "stop" to "run," even before I start the engine. I can start the engine up (on premix to be safe) and the alarm continues. I am thinking that since the alarm goes off regardless of the fact the engine is running, this would definitely point to either the failure of the float in the oil reservoir (this has entire oil reservoir under the cowling) or the electrical sensor unit. If it was an actual oil pump failure, the engine would have to be running for the sensor to sense "no motion" and trigger the alarm, right? Any good how too's on line with good write ups on how to trouble shoot this? I have a good multimeter.

Thanks, Benn

jimh posted 10-26-2006 09:39 AM ET (US)
Check your oil level sensor switch. There was a good discussion of a three-part failure of this circuit recently. The failure mode was quite astonishing:

--the floating magnet actuator became dislodged from the float;

--the reed switch which was to be actuated by the magnet was failed;

--the alarm module which was to be actuated by the switch was failed.

So all three portions of the alarm system (mechanical, electrical, aural) were failed!


Mercury Oil Tank Level Sensor

That article has pictures of the failed float switch mechanism.

bill705 posted 10-26-2006 02:07 PM ET (US)
An easy way to check it is to just take the screw holding the reed switch sensor underneath the tank out and slide the sensor out. No oil is going to come out with the sensor, it just fits up into a tube. Then turn the key on and see if it beeps. If if doesn't beep with the sensor out, slide it back in with the key still on and if it starts to beep when the sensor is inserted, the float is stuck or the magnet has come off. If it beeps with the sensor out, disconnect one of the leads from the sensor to the module and see if the beep stops. That will tell you if it's the sensor or the module.
Check the oil lines for cracks and leaks after you've fooled with it cause they do break and fall apart really easy.
Good Luck:
bill705 posted 10-26-2006 02:17 PM ET (US)
Forgot to mention that if it is the magnet and I don't really think that the float can get stuck, it takes a new tank to fix it. The tube and float assembly look like they're put in after the tank is built and are permanent.
It's a pretty easy job to replace the tank and bleed the oil line.
ttmac182 posted 11-07-2006 01:37 PM ET (US)
Just bought a 1995 2.5 Mercury 200 horse outboard. I took it to the local dealer to have the carbs cleaned and he suggested unhooking the oil injector and mixing the fuel. The alarms appears to work properly. Is this a good idea? Thanks!
Buckda posted 11-07-2006 02:20 PM ET (US)
It's a good idea for him if he's selling oil. Mixing straight (50:1) oil means that he's going to sell about 35-50 percent more oil to you.

If you are worried about the injection system, I'd just inspect the on-powerhead oil resevoir level before and after each use. If it stays full, you're in good shape.

alfa posted 11-07-2006 02:27 PM ET (US)
I agree with Dave.
I suggest to search for a professional Merc Dealer.
andygere posted 11-07-2006 07:45 PM ET (US)
ttmac182, I had the 1989 2.4 liter version of that motor, and an oil system failure is what killed it. The good news is that it could have been prevented. I would suggest that a qualified mechanic look at all the oil delivery components, and replace all the soft components (all of the clear and black tubing in the system) and carefully bleed the system. I recall the shop manual reccomended running on 50:1 from a portable tank after making these repairs to be sure all the air is bled out and the system is working. Oil injection is quite reliable in general, but it does rely on some very cheap parts that can easily fail and cause your engine to have a catastrophic problem (eg bearing failure, cylinder score, etc.). Replace these parts, and your chances of failure are pretty low.

That said, the pre-mix 1979 Johnson 85 on my old Montauk is still being run by the guy I sold it to several years ago. If premixing makes you feel more comfortable, there's nothing wrong with it. It was done for a long time before oil injection was invented.

PeteB88 posted 11-07-2006 07:59 PM ET (US)
I keep hearing certain year Merc and Yamaha were the same or same power heads - any chance my 92 Yamaha 40 3 cylinder is same as Merc? Nice to know as I continue to trouble shoot.


The A Dog posted 06-10-2007 11:41 PM ET (US)
Awesome info! New boat owner here with the opposite problem of most; my alarm won't sound on startup (when switching from off to run the alarm doesn't do it's diagnostic beep). The under-cowl oil tank is filling up and I have lots of bluish smoky exhaust, so it seems to be getting oil. I am a bit confused as to the testing procedure that's been mentioned...does the alarm generate beeps from its own speaker or is it tied into the boat's electric horn? Sounds dumb, but I don't know what it's supposed to sound like so I don't know where to test to see if it's just the connection to the sound-making part of the alarm. I'm hoping I'm not in for an expensive alarm module swap.

Also, has anyone fixed their cracked oil caps rather than replacing them? While trying to figure out the alarm problem, opening and closing the engine oil tank a couple of times to make sure it was filling and the float switch was working caused the cap cracked in half! Ugg, things are breaking faster than they're getting fixed! The instructions posted here said to make sure the oil caps were on tight...guess I overdid it. So I glued the halves back together with CA glue (cyanoacrylate, AKA super glue) because I was impatient and there's no way to get parts on a Sunday evening! This seems to work fine while idling...I didn't test it under load. Do you think this will work or am I setting myself for an oily explosion come high RPMs? It's just lame to have to have to order the whole 48 dollar cap assembly when all I need is the cheaply made plastic cap. I'm tempted to measure it, count the threads, and see if I can find something the same size to replace it.

Thanks for any help!

merc125 posted 06-11-2007 05:30 AM ET (US)
A new cap is $15 to 20 on ebay, mine has a float.The engine has its own alarm horn. Mine is wire tied to the engine wiring harness where it meets the guage clusterunder the dashboard. Tan/blue wire running back to the engine and purple from ignition switch. Some horns are mounted in the binicle or remote control. What engine do you have? MartyD
The A Dog posted 06-11-2007 10:06 AM ET (US)
Ok that helps a lot, I think I saw the alarm horn you spoke of last night when I was looking behind the dash. The engine is a 1985 150hp Black Max. Should I test the alarm horn with a multimeter? If so, what kind of voltages should I expect? Thanks so much!


tbg111 posted 06-20-2007 11:00 AM ET (US)
I think someone out there might be able to help me with this. I have an 1989 Mercury Mariner 100-HP that the oil warning alarm won't stop. I've disconnected the sensor leads and it still beeps. I replaced the warning module and it now sounds continuously (doesn't beep anymore). This has all been done with out starting the engine.

If the sensor were bad I assume that disconnecting it would have worked. I'm trying to diagnose this without going to the dealer because I would like to get the boat out this summer.

What are the components of the oil injection system that might cause the [this behavior]? I would assume by what I've tested that it isn't the sensor in the oil tank or the tank or the warning module.

What other components are there in this system?

Thanks for any response.

Ouroboros posted 07-17-2007 02:29 AM ET (US)
I have had the same beep - beep - beep [behavior] with my 1989 Mariner 75, and [to perform a] good quick test to see if it is as simple as the magnet coming dislodged from the float inside the oil tank, remove the few bolts holding your oil reservoir in place and turn it upside down with your key in the ON position. In my case, the beeping stops immediately, and returns as soon as I right the tank. As is stated in a few replies in this thread, there is no way to repair this magnetic sensor in the oil reservoir with any ease, so in my case a replacement of the oil tank itself will probably be done. I am confident that the motor is burning oil due to the smoke it emits, and that the oil level does drop after a day on the lake, so in the meantime I have chosen to disconnect the sensor until the tank is replaced. I am debating whether or not to remove the tank, flush it to remove oil, and drill a small (maybe 3/4") access hole close to where the sensor is to see if I can epoxy the magnet back to the float and the place a 3/4 plastic threaded plug in the access hole. I think if I pinch off the oil line exiting the tank before I remove it, I can save myself having to flush the air out of the system at the same time. Any thoughs on whether I should try this before shelling out the money to fix someone elses bad engineering?
robgoodwin posted 08-18-2007 04:46 PM ET (US)
I have a 1989 Mercury 150 that just recently started the Beep, Beep, Beeping while the engine is running. I checked the voltages according to the book and they all look ok. I've found when I start the motor and grab the motion sensor and wiggle it around I can get the beeping to stop. Does this really mean that the motion sensor is bad?

Also, I removed the oil inlet line to see how much oil was pumping out. Very little oil comes out, but more tends to come out with more rpms. How much oil should I see come out of this hose?

Thanks for any help.

scmaalna5 posted 08-22-2007 10:47 AM ET (US)
This is my first post I just found this great resource. I have a 1992 150 Merc on my 19ft Proline and I was out the other day and the beep, beep, beep went off. I looked at the level and it looked ok but. So I restarted it and it beeped again. It seemed to loose power. I only ran it for less than a minute with the alarm going off. I decided to not take a chance and called the tow company, ouch, I should have gotten the insurance. One piece of information that may be important, when we started the trip the oil tank cap was hissing because it was loose not really understanding the system was pressurized (this was prior to reading all the great info on this board)so I opened the cap while it was running. It made a little mess, not sure this could have caused the problem but it seems like kind of a coincidence. I should note that we ran out at 5000rpm for 12 miles after this then we trolled for about an hour with no alarm. Also the alarm came on after shutting down during a pass to change lures so it never was running at more than idle when the alarm came on. I have a few questions:

1. Assuming worst case scenario and the oil pump went would running the motor twice for less than a minut been enough to cook the engine?

2. Is there a run safe mode if the oil pump sensor causes the alarm, could this have caused the loss of power?

3. How difficult is it to bypass the system and go to premix? My logic is if it is going to cost me up to $2,000 to fix it it is just not worth putting that kind of money in it if I could just premix.

Tom W Clark posted 08-23-2007 10:03 AM ET (US)

1. No, running a motor for only a few minutes will not "cook" an engine.

2. No, there is no "run safe mode" on your 1992 Mercury 150. That is a feature found on OMC/BRP motors.

3. I believe the conversion to running premix is simple and straightforward but having never done it, I do not know the details.

Tom W Clark posted 08-23-2007 10:05 AM ET (US)

I would certainly think the motion sensor on the oil pump or the oil pump itself is suspect.

Yes, the oil output of the oil pump will vary with the RPM. That is why the oil pump is linked to the throttle linkage. You would have to quantify how much oil is "Very little" before concluding if that rate is normal or not.

scmaalna5 posted 08-23-2007 09:16 PM ET (US)

Thanks for the feedback. Did some checking today. I bought an external tank and gas line so I can run it on premixed fuel while trouble shooting. It seems to be running OK going to do a compression test when I get home from vacation just for peice of mind. I took the oil pump off today and turned the motor over by hand and pushed against the drive slot to see if the nylon gear is OK. It seems to be working fine so that's good news. I believe that is the most expensive fix so I'm going to test the components next. I also bled the system by losening the cap on the engine mounted tank it worked as expected but didn't stop the alarm. One question on the oil pump, I disconnected the oil hose leading from the pump to the fuel pump and then started the engine. I didn't know what to expect but the oil barely came out. Does that sound right?

robgoodwin posted 08-24-2007 10:00 AM ET (US)
To quantify, I ran the motor at idle on premix fuel and removed the outlet line from the oil pump. I measured 1 tsp in 2 minutes at about 800-1000 rpm. I don't know what the fuel rate is, but this seems like enough oil.

Also, after wiggling the wires on the motion sensor and getting the beeping to stop in the back yard, I took it out on the lake with no beeping for a few minutes. Then it would start beeping for a few seconds and stop if I increased the rpms a little.

gss036 posted 08-24-2007 01:56 PM ET (US)
One word of caution, if you remove the probe for the oil pump and take the magnet out, remember there is a north and south pole for the magnet. Make sure you put it back in the way it came out. If you can wiggle the connections and get results, you probably have a loose or bad connection.
frank_king posted 08-24-2007 11:55 PM ET (US)
Hey scmaalna5,

Its very easy to remove oil injection. Its been a while since I removed oil injection so bare with me.

Remove oil tank and two lines that come from boat and hook to engine.
Remove the check valve on the side of the engine that the oil tank gets pressure. Install a 1/2" pipe plug.
Remove engine mounted oil tank.
Remove the oil gear from engine. The best thing to do is to install the oil gear plug available at local mercury dealer. Installing the oil gear plug prevents a brass bushing from falling out of its desired position.
Remove oil warning system boxes and oil gear magnetic pickup from engine.
If the engine is and EFI engine then you must plug the hole in the bottom of the fuel tank that came from the oil gear. Its a 1/16th pipe thread.

(This is where my memory gets foggy)
And if anyone can correct me please do.
There is a brown with blue strip (if I remember correctly) that must be relocated on the starboard side electronic panel. what happens is the wire that ran through the oil warning system (thats been removed) is put on the terminal that leads back to the buzzer.
What then happens, is that the buzz that was heard when you first turned the key to the on position, doesn't sound any more. But the over heat alarm still sounds when an overheat condition exist.

The oil system works on the idea that at idle the mixing ratio is 100 to 1. When the throttle advances and oil gear arm is advanced the system now is at 50 to 1.


Tom W Clark posted 08-25-2007 12:15 AM ET (US)

One teaspoon over two minutes is not enough oil for you 1989 Mercury 150. The rate of oil consumption would be a 100:1 only if your motor burned about 3/4 of a gallon of fuel per hour. I know my 1989 Mercury 150s burn about 2 gallons per hour and even that may be a bit optimistic.

Tom W Clark posted 08-25-2007 12:19 AM ET (US)
I know my 1989 Mercury 150s burn about 2 gallons per hour (at idle) and even that may be a bit optimistic.

I suspect your oil pump is failing. If a tooth or two on the plastic gear breaks, the oil pump may operate sporadically. Dale, my Mercury mechanic, has told me he has seen this on several motors and it can lead to an intermittent alarm.

tmann45 posted 08-25-2007 08:49 AM ET (US)
One teaspoon over two minutes is not enough oil for you 1989 Mercury 150. The rate of oil consumption would be a 100:1 only if your motor burned about 3/4 of a gallon of fuel per hour. I know my 1989 Mercury 150s burn about 2 gallons per hour and even that may be a bit optimistic.

Tom Clark, please check my math:

My converter program says there are 768 teaspoons in a gallon. I agree with your 2 gph for fuel flow rate at idle as my FloScan reads +/- 2.5 gph for a 200 hp carb Mercury.

So, 768 teaspoons/gal X 2 gph = 1536 teaspoons/hour fuel usage. At 100:1 fuel oil ratio, 1536 / 100 = 15.36 teaspoons/hour oil usage. 15.36 teaspoons/hour / 60 minutes/hour = 0.256 teaspoons oil/minute or 0.512 teaspoons for 2-minutes at idle. Therefore it appears that the fuel oil ratio is actually 50:1.

So, 2 gal/hour X 768 teaspoons/gal = 1536 teaspoons/hour fuel usage. At 100:1 fuel oil ratio, 1536 / 100 = 15.36 teaspoons oil per hour. 15.36 / 60 minutes/hour X 2 minutes = 0.512 teaspoons oil for 2-minute run at idle. Looks like the fuel oil ratio is more like 50:1 for Rob's test.

Best Regards,

Tom W Clark posted 08-25-2007 12:09 PM ET (US)

Your math is correct. Mine was wrong. I had failed to make the conversion from two minutes to one hour and was using the number for a fluid ounce instead of a teaspoon.

Yes, it looks like one teaspoon in two minutes is actually a mixture slightly richer than 50:1 which is odd given that the oil is supposed to metered at 100:1 at idle.

Tom W Clark posted 08-25-2007 06:06 PM ET (US)
Regarding gss036's comments about the magnet, yes, the magnet has to go in one way and not the other. The end of the magnet that attracts the North arrow of a simple compass is the end that is inserted FIRST.
scmaalna5 posted 08-26-2007 10:03 PM ET (US)
Thanks for all the help. I spent today doing some checking on my 150. I actually have two 150s, one is a 1992 on my Proline 192 Dual Console (this it the one I am having the problems with) and the other is a 1988 150 XR4 on my Bass Tracker 1800 FS bass boat. The bass boat has already had the oil injection removed by a previous owner. Based on what I can tell all he did was disable the alarm and left everything in place and just started to premix. This winter I'm going to do it right based on info from this board. Anyway, back to the Proline, I spent today swapping parts from the Bass Boat to the Proline and trying it. I couldn't get the alarm to stop. I realize that one or more of the parts on the Proline are most likely bad (probably the reason that went to premix) but I just wanted to give it a try. While doing this I was running her on a premix tank. I want to get back on the water and considering that I spent $350 the other day for a tow I'm thinking I'm just going to switch to premix and get back on the water for little or no money. From what I read I can't see many reasons not to go to premix. The two bad things:

1. More smoke at idle - not a big deal to me

2. Higher oil consumption which means more cost. Unfortunately I don't get to use the boat that often (plus I split time between the two boats depending on the type of fishing I'm doing) so It would probably take me at least five years to recoup the cost I will spend to fix my problem in oil savings.

So with that said, am I missing anything else? Are there any other reasons what I should just do it? Thanks again for all the information.

Tom W Clark posted 08-26-2007 10:28 PM ET (US)
For me the biggest reason of all to maintain the oil injection is the freedom to just fill the oil tank and not worry about mixing the oil with the gas when I fill my gas tank. I have a 140 gallon gas tank and it takes enough time to full it as is. Having to slowly add oil while I'm filling would be a hell of a chore especially when trying to keep track of the ratio.

In the old days, you could buy "pre-mix" but I haven't seen that in 20 years around here. I would not buy if it was still available because the quality of the oil is so important.

If you have a smaller tank it might not be a bad idea to just run a gas/oil mix.

scmaalna5 posted 08-27-2007 05:38 PM ET (US)

You bring up a good point and raise another question. My plan was to figure out how much gas I was going to put in and dump in the oil first then put in the gas. I don't run great distances at a time so typically I put in 20 gals at a time (I have a 70 gallon tank). If I take this approach will the oil get mixed with the gas adequately? Just another thing I need to consider.

Tom W Clark posted 08-27-2007 09:30 PM ET (US)
To ensure that the gas and oil are mixed, the accepted technique is to use a funnel with a fine mesh screen in it. Simultaneously add the oil and the gas and it will enter the tank as a mix. This is basically a three or four handed operation unless you go *really* slowly.
scmaalna5 posted 08-28-2007 10:50 AM ET (US)
Wow, maybe I better pursue the fix that could be a real pain even with just 20 gallons or so.
scmaalna5 posted 09-05-2007 02:59 PM ET (US)
Flycast47 stated:

As mentioned elsewhere, the oil pump motion sensor should produce a 5-volt pulse every two revolutions. In order to do this [the oil pump motion sensor] must be getting 12-volt input from the white wire connecting it to the warning module when the ignition is on. You must verify that the 12-volt source is present before checking for the 5-volt pulse. If it is not, then the warning module is probably defective. If some voltage is available when checking the white wire (the negative lead of the volt-ohm meter is connected to a ground on the motor) you may still verify the presence of a pump sensor pulse though it will not be a 5-volt pulse. To produce the pulse the engine must be rotated with the emergency starter rope and the flywheel. with the spark plugs removed.

I had some time last night and tested the white wire coming out of the alarm module connected to the oil pump sensor. The purple wire going into the module was hot when I turned on the key the white wire that connected to the oil pump sensor remained dead. Based on this test can I assume that the alarm modual is bad?

scmaalna5 posted 09-14-2007 06:59 AM ET (US)
Well I'm at wits end. I decided that since my engine is 15 years old and in excellent shape (it's been well cared for and had little use and looks new) it might not be a bad thing to replace all of the electrical components so I changed out the cap, the pump sensor and the alarm module and guess what BEEP, BEEP, BEEP, etc. I also confirmed that the drive gear is driving the pump.

HELP I'm at a loss if I replaced everything what else could it possibly be?

Randy22 posted 09-14-2007 12:26 PM ET (US)
I was running into the same issues. I also replaced the oil cap and alarm module and the beeps would not go away. I finally took it to a dealer and he confirmed by worse nightmare, the gear was gone and there was no oil going to the engine. I had pulled the oil hose with the motor running on premix and go some oil coming out, but evidently not enough to satisfy the alarm module. And not that I did not trust the guy and his $2000 estimate for both engines, but I wanted to look for myself, so I removed the oil injector and pulled the gear bearing and drive shaft and the shaft was covered with plastic shavings. Hopefully when I reinstall a new electrical injection system this weekend, the beeps will stop. I have a post just below yours and I'll let you know what happens this weekend.
scmaalna5 posted 09-14-2007 10:55 PM ET (US)

After I confirmed that the pump shaft was turning I pulled it out to check the gear. The gear looked perfect and there were no plastic shavings on the gear. I'm thinking that the gear is okay.

Geoffers posted 12-17-2007 05:09 AM ET (US)
Just wanted to add my findings to this very useful site.
I started to experience the 'Beep Beep Beep' earlier this year on a 1995 135 Black Max. At cold there would be no problem but after 10 minutes or so it would start. Occasionally it would stop but not too often. Same again next day and so on...
After reading the info on this site I confirmed correct operation of the oil pump and found the problem to be the 'module'

Another score for the module!!!

New module cost me $180 from a mercury dealer.

Thanks all for the good info...


jimh posted 12-17-2007 10:12 PM ET (US)
Geoff--Thanks for adding your experience to the collection in this discussion. I am sure others will find it informative.
warlo_527 posted 03-04-2008 02:48 AM ET (US)
I hate to bring this post back up to the top, but don't want to create another topic!

I have a 99 Mercury Sportjet 175. (Serial # is OE3535xxx) I have disabled the oil injection and am currently mixing with synthetic at 50-1. I don't mind mixing and it gives me a little peace of mind. The only problem is I haven't figured out how to disable the alarm. I have spoke to many mechanics..all the local ones have no idea, and I have been given answers online of it's not possible with the [unclear].

I see that Frank had a reply that I haven't tried yet and don't quite understand.

"(This is where my memory gets foggy)And if anyone can correct me please do.There is a brown with blue strip (if I remember correctly) that must be relocated on the starboard side electronic panel. what happens is the wire that ran through the oil warning system thats been removed) is put on the terminal that leads back to the buzzer. What then happens, is that the buzz that was heard when you first turned the key to the on position, doesn't sound any more. But the over heat alarm still sounds when an overheat condition exist."

Not sure if this applies to engines with TKS. If it does not sure where I connect the brown with blue stripe wires plugs into?

Any techs who can help me in disabling the oil injection alarm only while keeping the overheat would be GREATLY appreciated...the buzzing is getting old!

dp463 posted 03-08-2008 08:18 PM ET (US)
I have a Mercury 200 EFI. Started the beep,beep,beep. I did a series of checks and replaced the alarm module. I ran the boat for about an hour and a half with no alarm. As I started to load the boat up at idle the alarm went off again. I came home and did a series of checks and noticed that the oil reservoir (under the cowl) was almost empty. The remote oil tank is full. I have checked hoses for kinks. Is there any way to check the small check valve? or are there any other things that could be the problem. Engine is getting oil just not pumping from remote tank to reservoir tank. Any help would be greatly appreciated.
Tohsgib posted 03-08-2008 08:50 PM ET (US)
The disconnect wires you should see towards the front of the engine, not the tan ones on the head for overheat alarm...just yank the harness. This is all I did on my OMC and beep still goes on at initial key turn. You can then test your overheat alarm by disconnecting the sensors and "possibly" having to ground them to engine for a test.
deepwater posted 03-08-2008 09:15 PM ET (US)
you said you disabled the oil injection ,, does that mean you drained the oil tank too,,, if so is that the alarm your hearing (low oil),, if so could you fill the tank with oil (enough) to silence the alarm ,,I am not real technical about things sorry
Welder08 posted 03-09-2008 04:10 PM ET (US)
I have a 1988 135 HP Mercury with oil injection. Runs great but seems to smoke quite a bit at startup. I checked the oil pump linkage and is set to correct indent at idle. I'm running Mercury Premium Plus oil and was wondering if this smoking is normal or is the something else I could check.
L H G posted 03-10-2008 02:43 PM ET (US)
Check for a worn out oil pump. As they wear, they let more oil through as a fail safe measure, causing the excessive smoking. I have an 1988 150 2.0 liter, basically the same engine as yours, and that was my problem.
Welder08 posted 03-10-2008 05:17 PM ET (US)
That's what I was thinking it might be as it doesn't smoke when boat is up to speed and runs great. Will check out new oil pump. Is it a big deal to install? I'm no Boat mechanic but looks like just 2 bolts hold it in.
tmann45 posted 03-10-2008 06:38 PM ET (US)
Welder, if your engine has a thermal air valve (carb models), you might want to check it. It will make the engine run rich if it is not opening once the engine is warmed up.
Welder08 posted 03-11-2008 07:02 PM ET (US)
Thanks for the info tmann.
Seems to only smoke when I first start the engine, whether it's a cold or warm engine which leads me to believe it's running 50:1 at startup instead of 100:1. I'll check for thermal air valve. I know these oil pumps are a bit pricey. Cheapest I found was around $170.00. Is there a chance the oil pump could just be dirty and all it needs is a good cleaning? The engine is 20 years and even I've needed a good cleaning in that span!

Great forum and THANKS for all the info.

kmc posted 03-21-2008 05:11 PM ET (US)
First time on here. I read through this thread but couldn't find my answer

I have twin 1999 Mercury V150 motors. Starboard oil alarm came on. It is a non-stop beep-beep-beep that does not stop until I turn the key off. Much different than the steady beep for the over temp alarm. One at a time, I swapped the oil cap, motion sensor, warning module, and oil pump. Same problem on the starboard and no problem with the port engine after I moved all the parts over.

I manually turned the pump and oil did flow through. The gears are in good shape. With the engine running I disconnected the hose and 3 drops of oil came out in less than 10 seconds.

I disconnected the motion sensor and started the motor and did not get the warning. While the engine was running I reconnected the sensor and it triggered the alarm.

I pulled the motion sensor out of the hole, reconnected it and started the motor. No warning alarm until I put the motion sensor back in the hole. I swapped motion sensors again with the other engine and same problem.

The alarm does go through its cycle when I turn the key on.
I do not have a water sensor attached to the fuel filter.

Any idea why I'm getting the low oil alarm?


bigshrimpin posted 03-23-2008 12:34 AM ET (US)
There is a $16 fix for all [Mercury Oil Injection] problems. You can buy plate and gasket to cap off hole in the crankcase and just premix. You just have to remove the shaft, oil pump, oil tank, the module, and cap off. Premix 50:1 and [your are] done forever with these Mercury oil injection headaches.

Stay on top of the carbon buildup with a couple cans of power tune every 100 hours. While [you are] at it, junk the spark advance module and the idle stabilizer, set the timing manually,and now your Mercury will last forever--as long as you keep an eye on the wiring.

jimh posted 03-23-2008 03:27 PM ET (US)
Keith--Since you have swapped all of the electrical components in the system, and the alarm condition persists, I suspect that the cause of the alarm condition is a mechanical problem. Perhaps the drive shaft from the crankshaft gearing is not turning at sufficient speed--just a guess.
gss036 posted 03-23-2008 04:44 PM ET (US)
{One word of caution, if you remove the probe for the oil pump and take the magnet out, remember there is a north and south pole for the magnet. Make sure you put it back in the way it came out. If you can wiggle the connections and get results, you probably have a loose or bad connection.}
"Tom Clark" "Regarding gss036's comments about the magnet, yes, the magnet has to go in one way and not the other. The end of the magnet that attracts the North arrow of a simple compass is the end that is inserted FIRST"

This an earlier response w/comment by Tom Clark. If you have not messed w/the magnet and then you put everything back together right and still get the alarm. I would only assume that the pick up sensor is bad for some reason. These things work on the same principle as old spedo controls,:counting evolutions.

DaveLewis posted 04-04-2008 06:11 PM ET (US)
New to this forum.

I have a pair of Mercury Optimax 150 new in April 2005.
I get 4 beeps every 2 minutes. There is no water in the fuel filter. Last time this happened the dealer replaced the oil reservoir assembly 833069T9 saying that the sensor was bad but it was built in to the tank so they could not just replace the sensor.

At this site:
25 856156A2 SWITCH ASSY 1 Info $13.90
19 833069T9 RESERVOIR ASY-OIL 1 Info $86.01

Appears that the switch assy 856156A2 is replaceable in that one screw with a washer on it holds it in the hole. Remove the screw and the switch slides right out.

My question is, can just the switch be replaced to make the fix (stop the beeping) or does the whole oil reservoir have to be replaced every time?

Thank you.

kh4 posted 06-08-2008 09:52 AM ET (US)
Dear Continuous Wave,

I have a 1996 mercury 150XR6.I resently went to the lake and when I was turning the engine over the oil alarm sounded immediately and would not start. I was at the lake less than two weeks ago and everything was fine. I have oil in the oil tank and in the reserve tank. Any help would be gratefully appreciative in trouble shooting. Before I take it to the shop. Thanks, KH4

sosmerc posted 06-08-2008 12:02 PM ET (US)
Make sure your "kill switch" toggle is in the "run" position.
jmwilson posted 08-07-2008 11:36 AM ET (US)
I have a 1998 518 Ranger with the same year 200 HP EFI Mercury that I bought new in October 1997. The engine has about 6 gallons of oil ran through it. I was at the river a few weeks ago and the beep beep beep oil warning alarm started going off, so I loaded it up and took it to an authorized Ranger Mercury dealer. He called me yesterday and said my crank shaft oil pump gear was damaged. I have decided not to spend the 1200 to 1500 dollars to put another plastic gear on it. I am going to pre mix my oil and gas.
If it is any help to you guys, here is what I am going to do. At a 50 to 1 ratio, I will multiply 2.56 times the gallons of gas I put into the tank. This will give me the ounces of oil I need to put into the gas tank to get the 50 to 1 ratio I need.
The dealer I bought this rig from told me I would eventually have to make the decision to pay for an expensive oil pump repair bill or pre mix the oil and gas. I cannot believe Mercury used a plastic gear like this.


jimh posted 08-07-2008 01:35 PM ET (US)
Mike--Thanks for your report of the failure of the plastic gear used to provide the mechanical drive for the oil pump in your Mercury motor's oil mixing system. Unfortunately your experience is fairly common, and, as you have learned, the remedy is very expensive. Replacing the existing plastic gear with a new plastic gear really does not eliminate the chance that it will fail again--it's just a plastic gear after all.

You ought to consider changing to the electronic oil injection system that I mention above in this discussion. It is a much better solution than the OEM plastic gear, and much better than pre-mixing if you have a large volume tank.

njwhaler posted 08-08-2008 07:32 AM ET (US)
I am having problems with my 2002 Opti 135. The alarm went off (4 beeps every two min)and my reservoir (large reservoir in the transom, not the reserve on the motor) was full. Actually, I filled the oil reservoir, ran the boat for 10 min, then the alarm began to sound.
Now, here is what concerns me. I called Mercury and the rep on the phone said 4 beeps can only be the sensor at the cap. He told me to tighten the cap. If that didn't work, then all I needed was a new cap/sensor.

I asked him if it could be anything else because I am worried about oil not getting to the motor. He said no, if you have oil in the tank, then you are good to go.

After reading the posts, I am concerned whether this guy has given me accurate information.

jmwilson posted 08-12-2008 01:47 AM ET (US)

I am going to pre mix my fuel for now jimh. I do a lot of fishing in stumpy lakes, so I do most of my running at an idle speed. If the motor bogs down as I get up on plane or the plugs foul easily, I am going to put the electronic oil ejection system you talked about on my engine.


DeeDee posted 09-14-2008 12:33 AM ET (US)
Hello Gentlemen...I hope you'll be able to share your wisdom on an issue I am having with my 95 Mercury 200hp. She started the..Beep...Beep...Beep, so I check the oil and it was a little low, so I filled up the remote tank. The reservoir under the cowl was full. Started her up and the beep..beep still continued. Shut her off and checked to make sure the sensor wasn’t stuck and then she wouldn’t start again. After 20 plus cranks, she started with the typical smoking that old Mercury motors do, but the beep...beep was still happening. So, I have her towed (to be safe), try to start her when we get back and again it takes 20 cranks. With her being so hard to start, it seems unlikely that this is a simple sensor issue. But what else would cause her to not want to crank? I’m a lady who needs some education on the matter so I can speak intelligently with the marine mechanic. Thank you guys for your help!
seabob4 posted 09-14-2008 03:52 PM ET (US)
There is a $16 fix for all [Mercury Oil Injection] problems. You can buy plate and gasket to cap off hole in the crankcase and just premix. You just have to remove the shaft, oil pump, oil tank, the module, and cap off. Premix 50:1 and [your are] done forever with these Mercury oil injection headaches.

Stay on top of the carbon buildup with a couple cans of power tune every 100 hours. While [you are] at it, junk the spark advance module and the idle stabilizer, set the timing manually,and now your Mercury will last forever--as long as you keep an eye on the wiring.

That's the fix! A plastic gear to drive the most important pump on your motor, and it's buried deep inside a hot engine block. Thanks, Merc.

fleedermouse posted 09-19-2008 03:43 AM ET (US)
The referencd article refers to a "troubleshooting chart following" but I don't see one anywhere. Where am I missing it?

I have had [a problem] with the warning horn emitting "BEEP-BEEP-BEEP" after repeated tries at starting or restarting engine. I get the initial beep when turning key to on position. I'm guessing that there are some tiny air bubbles forming or something because the problem goes away if I turn off the battery and give it a few minutes. Also, my oil consumption appears to be steady.

jimh posted 09-19-2008 09:05 AM ET (US)
From the precis of the article:

"This brief excerpt is presented in order to provide a point of reference for comparison of the Mercury system of oil injection with other techniques used to accomplish mixing of oil and gasoline in two-cycle outboard motors."

The article does not include the troubleshooting chart material from the Mercury literature. It is just an excerpt from the manual, not the whole manual. The article is not intended as a source of diagnostic advice, but rather as an illustration of how the system is designed.

As mentioned previously regarding interpretation of the sounding of the aural alarm of the Mercury Oil Injection system:

If the alarm is a BEEP BEEP BEEP, it is an oil alarm, and is caused by either:

--oil level float switch in reservoir

--magnetic sensor in oil mixing pump input drive shaft has stopped rotation

--a defect in the alarm module itself (apparently a common failure)

Because there are no indicators and the cadence of the alarm tone is the same, you have to deduce which sensor is causing the problem.

jimh posted 09-19-2008 09:10 AM ET (US)
I do not see a mechanism in which bubbles in the oil line can cause an alarm. As far as I can tell there is no sensor in the Mercury Oil Injection alarm system which actually monitors for flow of oil. The sensors only monitor for two conditions:

--the oil level in the reservoir is low

--the input shaft to the pump is not turning

Neither of these sensors monitor the actual flow of oil.

The only sensor which could be affected by air bubbles is the float sensor. If the oil in the reservoir were to become foamed, perhaps the float sensor might not operate properly. But I doubt that this is occurring since you describe the problem as happening at engine start, when the boat is not moving.

Tom W Clark posted 09-19-2008 12:38 PM ET (US)

Do not overlook the very real possibility that your alarm module itself has simply gone bad. This is a very common problem on older Mercury motors.

I have two 1989 Mercury 150s. I had an alarm module go bad two summers ago and it caused a great deal of distress until I figured out it was just the module itself which needed to be replaced.

The same thing happened this summer with the other motor. $200 for a new alarm module and the problem has been fixed...for now.

xenasomerset posted 11-22-2008 11:05 AM ET (US)
OK you guys, I read all of this and now would like to ask about this problem specific to our 2000 Mercury 30 HP outboard. We are getting the continuous warning, as soon as we turn the key, and we have the oil reservoir topped off. What should we do next? Thanks!
jimh posted 11-22-2008 12:20 PM ET (US)
Most Mercury alarm systems will sound a start-up beep sequence when the ignition key is turned to ON from OFF. The sequence is typically "DAH-Di-Dit" or "DAH-Di-Di-Dit" where "DAH" is a longer sound and "Di" or "Dit" is a shorter sound. If you don't get those start-up beep sequences there is likely a problem in the alarm module itself.

If you get a continuous BEEEEEEP after the start-up sequence, it should indicate an overheat condition. It the motor is stone-cold and has not been run, it cannot be an overheat condition, so such an alarm indicates a faulty sensor for the temperature alarm.

Because there is no specific signal given for what sensor is signaling an alarm, the best way to deduce which sensor is involved is to disconnect the wire going to each sensor, one at a time. If the alarm is silenced when a sensor is disconnected, it is a reasonable inference to conclude that sensor has signaled the alarm. If there is conflicting evidence that indicates no possibility exists for that alarm condition, you can conclude the sensor itself is bad. If the alarm persists even with all sensors disconnected, the fault is likely in the alarm module.

Also, electrical wiring can become frayed and cause short circuits. In some cases expensive repairs have been undertaken to remedy a condition caused by an electrical conductor being shorted.

In any alarm system, when an alarm is sounded, there are three reasonable possibilities:

--a fault condition exists, a sensor has detected it, and the alarm system is signaling this fault;

--no fault condition exists, a sensor has malfunction, and the alarm system is signaling an inappropriate fault condition;

--no fault condition exists, all sensors are operating normally, and the alarm system itself has malfunctioned, signaling an inappropriate fault.

xenasomerset posted 11-22-2008 02:16 PM ET (US)
OK, thanks, Jim. As I said before, the oil reservoir is full. Turning the key (with the engine cold) immediately produces the long uninterrupted beeeeep.

We disconnected the wire running from the oil level sensor to the alarm module. This action stopped the alarm. No more beeeeep.

So based on the logic you provided, I would say that it appears we have a faulty oil level sensor and the next course of action would be to replace that part, right? I believe that we can order this part and install it into the bottom of the oil reservoir, based on my Mercury troubleshooting documentation, can you confirm? It appears that on our engine, we could replace the sensor only, into the bottom of the oil reservoir from below, without having to order an entire new oil tank.

And we plan to go ahead and run the engine with this wire disconnected, keeping a close eye on oil reservoir level, until we can get the oil level sensor replaced. Make sense?

jimh posted 11-22-2008 02:58 PM ET (US)
If you inspect the float sensor in the under-cowling oil reservoir you should see that there are two elements to it:

--magnetically operated electrical switch
--magnet on a float in the oil tank

The problem can be with either element. It is fairly common that the magnet has fallen off the float, or the float has become saturated and no longer floats. The actual magnetically operated switch may be intact.

To be certain about the sensor, also try disconnecting other sensors to make sure they also do not shut off the alarm.

Does your alarm system sound the Dah-di-dit or Dah-di-di-dit signal at key ON?

xenasomerset posted 11-23-2008 07:02 AM ET (US)
It's just a continuous beep as soon as the key is turned - no breaks in the sound at all.
Dick E posted 11-23-2008 09:05 AM ET (US)
I just had xenasomerset's problem [a continuous beep as soon as the key is turned - no breaks in the sound at all] on my 1998 Mercury 90-HP. A sensor was bad. Also my oil reservoir had a crack in it too. Replaced the sensor and tank.

If you have the key on after you replace the sensor and start to fill the tank with oil the buzzing should go off.

If you need to run your boat before you get the sensor replaced you can add the appropriate oil directly to gas and when you are comfortable that the problem is fixed, just use the oil injection system.

jimh posted 11-23-2008 03:12 PM ET (US)
Dick--What sensor did you replace? Was it the under-cowling oil reservoir level sensor? If yes, it would be interesting to know if the float and magnet were OK and the switch malfunctioned, or vice-versa.
Dick E posted 11-23-2008 07:16 PM ET (US)
The low oil float sensor was bad- the magnet & float looked okay.
cordesw posted 01-06-2009 04:27 PM ET (US)
I have a 1998, 200hp Mercury outboard. It has operated very well for the last 9 years but this summer I had the alarm (beep, beep, beep) go off. It started off intermittently and then continued to worsen until it was on all the time. For the short term (and until I resolve the problem) I mix the oil manually 50:1 and monitor the reservoir. The reservoir looses a level which tells me the pump is working and the engine is getting enough oil.

Winter has arrived and I want to correct this before i get into the spring/summer/fall. I've concluded that my problem is the oil module, which I've read is a common problem. I went to the local boat shop and bought the module. The salesperson gave me the item and I went to install it on the boat. There are 2 halves to this....she gave me the bottom half...(the part numbers match). My question is this the only half I need to replace?

Any other thoughts would be appreciated

searayder175 posted 04-28-2009 03:04 PM ET (US)
Hello All, I very much appreciate all that this forum has to offer. I have a 1997 Seay Rayder 175 with an oil injection problem. After reading your great replies I determined the plastic oil injection gear is striped. After removing the pump I can actually turn the shaft easily with very little friction. There are areas on the main gear that seem to be partially intact. Maybe that is why at low idle the Beep Beep Beep was steady and at higher RPMs erratic. This may have saved the engine since the pump was working partially at high RPMS. I pulled off the pump and all of the injection components including the magnetic receiver and oil level warning device. I have looked everywhere on the engine for the Oil Warning alarm module “5 wires” to no avail. Interesting is that when I start the boat now with 50:1 premix the alarms sounds 4 beeps and stops returning in 4 minutes to the same 4 beeps. I would like to disable the 4 beeps and keep the over heating alarm. Your advise would be greatly appreciated. Thank You
vettedog72 posted 06-07-2009 08:29 AM ET (US)
My 1984 Black Max 150 motor had not been run for several years and required the carburetors to be cleaned before it would crank. I used pre-mix fuel when I started it; the oil pump seemed to be working.

I changed to straight gas, only to see the oil line from the oil pump appear as it were empty. When I squeeze the gas line primer bulb, I think I see gas running backwards into the oil pump feeder line. I will follow the instructions for bleeding the air out of the pump but I am curious about the one way valve that keeps gas from coming into the line. Is this something repairable; is there a valve that keeps the gas from coming in the line, what is it made of? Any comments would be welcomed. Thanks in advance for your comments.

jimh posted 06-07-2009 09:52 AM ET (US)
Refer to the illustration in the REFERENCE article. Refer to callout 6. The legend for the callout 6 says:

"2-PSI CHECK VALVE--This valve prevents gasoline from being forced into the oil lines."

From your narrative it sounds like gasoline is being forced into the oil lines. This implies a failure of the 2-PSI check valve. Replace the 2-PSI check valve.

vettedog72 posted 06-07-2009 10:40 AM ET (US)
Thanks for the info. I'll see if I can physically locate the valve, I think it must be hanging off the engine mounted oil tank or actually mounted on the tank. right?
BillW posted 06-12-2009 03:01 PM ET (US)
I am doing the premix conversion on my 1996 Mercury 200XL, the crankcase line coming of the engine to the remote tank, should this line be plugged and if so, before or after the check valve?


jimh posted 06-12-2009 08:57 PM ET (US)
Remove the whole enchilada. You don't need the pressure take off from the crankcase any more.
BillW posted 06-12-2009 09:34 PM ET (US)
Thanks, That is what I thought but wanted to make sure
mbrantl posted 06-13-2009 08:59 AM ET (US)
[This article was posted in duplicate both here and in another thread. Please, do not post your articles is duplicate.--jimh.]
kgaude posted 06-23-2009 02:01 PM ET (US)
I have read all of the posts and have an additional question to ask. I have a Mercury 150 EFI on a 1993 boat. I assume the motor is a 1993. The oil horn Beep Beep Beep started sounding this last weekend pretty much immediately upon leaving the landing. I have checked the oil reservoir cap under the cowling and it is working fine and the reservoir is full. If the float is down it completes the circuit. if up (full) there is no circuit. What I'm wondering is that the horn sounds upon startup and will turn off if the motor is run above idle and return when the motor returns to idle. Has anyone encountered this before? Is there a pressure sensor on the oil pump along with the rotation sensor. My plan was just to replace the alarm unit since it seems to be the likely culprit from most of these posts and it will be cheaper than a mechanic's debugging time but the alarm turning off upon revving the engine has me puzzled. The motor appears to be getting oil since it smokes when running. Any help would be appreciated.
KMflkeys posted 07-02-2009 11:09 AM ET (US)
Re diagnosis of oil alarm on a 1998 Mercury 135L: One test is to insert a probe into the blue/white wire between the motion sensor and oil warning box. It should fluctuate between 4-6 volts and below 1 volt. Mine reads 4.9 volts and does not fluctuate. Does this mean the motion senseor is bad or the pump is not turning? The book says no voltage indicates bad sensor but I do get a voltage reading. I intend to test the oil flow to see if the pump is moving and if so, is the sensor bad? Or could it be the warning module, like so many others on this post? At $260 I don't think I will replace it only to have it go out again. Thanks.
clubsled posted 07-15-2009 12:28 PM ET (US)
Hello All,
Thanks for all the useful information!
I have a problem with my 1995 Mercury 150 EFI. The condition is unique to any of the previous problems.
I bought the motor 6 years ago and had a problem with the low oil buzzer going off. After examination of the engine reservoir (low) i determined the buzzer was working the way mercury intended (truly a low level of oil in the engine reservoir). I replaced the cap seals in the remote oil storage tank and the problem was solved until now.
6 years later the buzzer started going off again. Same condition as before low level in engine reservoir. Replaced both cap seals in remote oil tank but this time the problem was not fixed. I remove the cowling loosen the engine reservoir cap and it will fill up the reservoir after 5 min. Put the cap back on run down the lake 10 minutes later the buzzer is going off again. I'm baffled, i have inspected all the lines for air leaks and do not seem to have any. It cant be an obstruction because when i loosen the engine oil reservoir cap the reservoir will fill up. It seems to me the remote reservoir is not pressuring up enough to get the oil to the engine oil reservoir. I just am at a loss of what could cause this.

Thanks in advance for any help you may offer.

smokeeatr12 posted 07-15-2009 09:58 PM ET (US)
I am needing some advise. I just recently went to the lake with my 1998 Mercury 150 EFI Outboard. While on the water a alarm began to sound when I slowed to idle at a fishing hole. The alarm was in the form of a beep, just like the beep when I turn the key on. Once I gave the motor the smallest amount of gas the alarm would shut off. But if at complete idle the alarm would sound. I ran the boat all day thinking it might be a low voltage issue. I have had the voltage checked all good. The boat is presently at a mechanic shop where he says the oiler is not working. He advised the gas in the motor still had oil in it. This tells me that the motor was oiling at high RPM. The mechanic says the gearing that runs the oiler in the motor is bad. This does not make much since. I feel that the unit is oiling but just does not at idle. He is wanting me to disconnect the oil system. I don't want to do that if it is a small issue. Does anyone know what would cause this issue. Once again it only alarms at idle not while running.
takrafft posted 07-31-2009 03:41 AM ET (US)
My -87 200 Black Max has had all the oil injection parts disconnected and removed. I am considering the possibilities to put it back in operation. I want to put in an electric replacement pump. I wonder if anyone can post some pictures of the internal and external oil reservoir, so I know what to look for on e-bay etc. when buying!!
jimh posted 08-02-2009 11:06 AM ET (US)
"The mechanic says the gearing that runs the oiler in the motor is bad."

It sounds like your Mercury motor has damaged its PLASTIC gear that runs the crucial drive shaft to the oil pump. Your choices are now as follows:

--give up on the oil mixing system, and resort to the 1930's technology of mixing gasoline and oil in the fuel tank. This is a reliable way to provide oil to a two-cycle motor, as long as you remember to add the oil. There will be no alarm system, so one tank of gasoline with no oil and your motor is probably ruined.

--pay your Mercury dealer about $1,200 to repair the PLASTIC drive gear. According to my local Mercury dealer, who has been working on Mercury motors for about 45 years, he cannot remember anyone ever doing this. This repair is just too expensive, and since the replacement part is another PLASTIC gear, the system is really not improved.

--buy a non-OEM replacement oil pump which is electrically operated. This system is designed by a former Mercury engineer--he was probably aware of the PLASTIC gear failure problem and saw an opportunity to improve it.

If you need details, read the previous articles in the thread. All the information has already been given.

rumrunner posted 08-03-2009 05:53 PM ET (US)
I had a perplexing (to me) problem develop today, and I thought I'd run it by forum members for feedback.
The subject is a 1997 Outrage 20 with a 1998 Mercury 175 EFI.
I was cruising for about a half hour at 3200 rpm, and experienced a sudden engine shutdown accompanied with a simultaneous oil alert (rapid beeping). I pulled the cowling, and noted that the engine (cowling) tank was full, cap tight with no signs of leakage. The remote tank was 3/4 full, no signs of cap leakage. There were no signs of oil leakage in the cowling.
I restarted the engine (alarm went thru normal start sequence, no issues), and it idled normally (without alarm) with no audible signs of trauma.
However, as soon as I advanced the throttle, the engine would shutdown at 1800 rpm, again accompanied by the rapid beeping oil alarm. These shutdowns were instantaneous, with no sputtering.
I managed to make the 5 miles or so back to the dock by staying below the 1800 rpm level. If I exceeded 1800 rpm, it would immediately shutdown with a low oil alarm. I monitored the oil on the way back, and the cowling tank stayed full throughout.
These symptoms don't seem consistent with a "classic" oil pump failure (which I have experienced firsthand, hence my paranoia).
With the cowling tank staying full am I correct to assume the pump is functioning (since the tank would have drained significantly on the return with a faulty pump, right?).
My instinct is to fault the ECM at this point, in absence of some of the aforementioned issues I have read in this thread.
Any feedback?
jimh posted 08-03-2009 06:06 PM ET (US)
The pump that transfers oil from the remote tank to the under-cowling reservoir is a separate and different pump than the pump that feeds oil into the fuel system. The tank could be full, and no oil would be going into the fuel system.

If you read the referenced article that begins this long thread, the system is explained in detail.

rumrunner posted 08-03-2009 06:12 PM ET (US)
OK, but with that said, any thoughts on everything functioning fine under the 1800 rpm mark, with an abrupt shutdown/alarm above that point?
rumrunner posted 08-03-2009 06:16 PM ET (US)
Better stated, will the cowling tank continue to drain into the pump even if the pump shaft was not turning? That's where my confusion is, and pardon my ignorance in advance.
Orbit Express posted 08-06-2009 10:33 AM ET (US)
I've been having the same problem, I think everyone should check and replace all the cheap plastic hose clamps going from small tank on top of engine to the various modules. I found leaks there where hoses connect to modules. Mine are not only loose, but some are cracked. I fact, a few years ago, my gas line came off because the cheap electrical tie wrap cracked, causing the hose to come off.

Just my $0.02

jimh posted 08-06-2009 12:28 PM ET (US)
In the Mercury automatic oil mixing system, the oil from the under-cowling tank is fed by gravity to the oil mixing pump. It is a nice, simple, reliable way to feed oil. It gives the system a reserve capacity of oil in the event that the engine crankcase vacuum pump fails and no longer pressurizes the remote oil tank. There is enough oil in the under-cowling oil reservoir to run the motor for quite a while, perhaps allowing you to return to port for repairs while still operating the motor. It is a nice design feature.

The oil mixing pump is turned by a geared shaft linked to the engine crankshaft. The pump is automatically primed by the gravity flow from the under-cowling reservoir. It pumps out oil to be mixed with the gasoline.

The oil level in the under-cowling oil tank can decrease via only two methods, at least the only two I can think of:

--there is a leak in the tank, hoses, or other fittings, and an unintentional flow of oil occurs; or,

--the oil mixing pump is operating and drawing oil from the reservoir.

Precisely what happens in the case of the oil mixing pump failing to operate is not clear. I suppose it would depend on the mode of failure of the pump. Perhaps there could be some failure mode in which oil from the under-cowling reservoir would continue to be drawn into the pump, but that is just speculation.

rumrunner posted 08-06-2009 11:01 PM ET (US)
Thanks for your responses. My big question was would the gravity tank also guard against a gear driven oil pump failure by continuing to feed even if the pump was not functioning.
Regardless, source of aforementioned problem- a corroded pin on the console to motor harness. Not a mechanical issue, thankfully. Harness plugs cleaned, and back to normal.
paynekk posted 08-08-2009 10:42 PM ET (US)
Not sure if this posted twice?? I have a broken hose on my Merc 135 oil system. I think it is the hose that delivers the pressure to the oil reservoir (main tank). It is broken off right near the tank. My question is? Do I have to replace the entire hose system from the reservoir and into the motor or can I splice (using hose and clamps) at the oil resevoir. It is broken right next to the main tank . I don't want to replace the entire hose if I don't have too
jimh posted 08-09-2009 07:47 AM ET (US)
I am not clear about which hose has broken. There are two hoses attached to the main oil tank. One hose provides only pressure. The pressure is developed from the engine crankcase pulses. The second hose provides the flow of oil from the remote tank to the under-cowling oil reservoir.

Either hose could be spliced by using a suitable barb fitting and clamps. However, it the hose is old and has deteriorated or been worn, replacement of the entire hose may be more effective at preventing future problems with the hose.

Johnbee123 posted 09-03-2009 11:26 AM ET (US)
Thank to all for some awesome info on oil injection. I just got a used boat with a 1992 150 Black Max. First out of the chute I replaced the water pump housing and impeller. Ofter that I have the infamous Beep - Beep - Beep on the oil sensor. My symptoms seem slightly different so I appreciate any troubleshooting suggestions.

1. I resealed the transom oil tank lids, seemed to help there was pressure in the tank when i loosened the lid.

2. No alarm at idle, alarm at moderate speed, no alarm at high speed/rpm. (this seems different symptomatically compared to others)

3. Could I have caused the issue by taking the lower end off the motor and replacing it (changing the water pump)?

4. I noticed that there seems to be a little spray of oil on the foam on the cowling, very little.

Note: my overheating problem was fixed with the pump kit. I had a great conversation with the service rep at Merc Headquarters, very nice and helpful.

Thanks for the help!

Johnbee123 posted 09-03-2009 11:40 AM ET (US)
Another question, is there ever a situation where you could be getting no alarm and still have no oil feeding the engine?
Tohsgib posted 09-03-2009 01:32 PM ET (US)
You can not mess up the oil injection by removing the foot or replacing the water pump.

"Another question, is there ever a situation where you could be getting no alarm and still have no oil feeding the engine?"

Answer...not for long ;)

Johnbee123 posted 09-03-2009 01:41 PM ET (US)
Thanks Tohsgib, any thoughts on why I am getting oil alarm at moderate speeds and not at idle or high RPM?
Tohsgib posted 09-03-2009 01:51 PM ET (US)
Quite common for faulty sensors on the Mercs(and others to be honest). Sometimes it is the plastic oil pump that is starting to go bad, usually too expensive to fix usually and people just disconnect and pre-mix. I had an intermittent alarm on my OMC and it turned out to be water in my oil tank. You could not see it until I drained it and the last Qt was milky blue. I disconnected and pre-mixed because I was tired of farting with it.
toolman posted 09-11-2009 10:43 PM ET (US)
Does anyone know why the mercury 225s dont have a motion sensor on the oil pump, only in the oil tank.
jimh posted 09-13-2009 08:29 AM ET (US)
As far as I can tell there is no sensor in the Mercury Oil Injection alarm system which actually monitors for flow of oil. The sensors only monitor for two conditions:

--the oil level in the reservoir is low

--the input shaft to the pump is not turning

Neither of these sensors monitor the actual flow of oil.

number9 posted 09-14-2009 09:36 PM ET (US)

To clarify toolman asked "Does anyone know why the mercury 225s dont have a motion sensor on the oil pump, only in the oil tank."

That motor does not have the sensor to warn "the input shaft to the pump is not turning" and is a rather good question.

jimh posted 09-15-2009 09:01 AM ET (US)
Distinct from what was implied in the question, there is no motion sensor in the oil tank. There are no motion sensors that monitor the flow of oil, as far as I have read or know, in the Mercury two-cycle motor oil alarm system described in the REFERENCE article, the topic of this discussion.

If the premise that there are Mercury 225-HP motor that lack the motion sensor for the input shaft of the pump is true, then apparently their the alarm systems consist of a single float level. Before taking that as gospel there should be confirmation. Curiously, it was recently suggested the newer Mercury oil systems were more sophisticated than the one described in the REFERENCE article, which is an older motor. I remains to be seen precisely what additional sophistication has been added. Removing a sensor does not seem to be a way to increase sophistication.

toolman posted 09-20-2009 12:19 PM ET (US)
I am wondering if my Mercury 1996 225 EFI has the same plastic oil pump drive gear? It only has the float level sensor in the oil tank, It has concerned me some but I havent seen any problems with this engine on here and wonder if the system is more dependable. It also appears that the 250 EFI models dont have a motion sensor on the oil pump shaft either. I am just wondering if anyone has any imput on these model engines and the oil injection warning systems on them. Thanks
jimh posted 09-20-2009 01:40 PM ET (US)
My impression of the overall reliability of the plastic gear drive system (used to provide the oil pump shaft input motion) is it is generally not a problem when the engine speed is held to moderate levels. For people who run these Mercury engines at 3,000-RPM most of the time, there are few reports of failure of the plastic gear. Failure of the plastic gear seems to me associated with high engine speed operation. Again, this is just my impression. I have absolutely no statistical data to confirm this.
Tom W Clark posted 09-21-2009 06:19 PM ET (US)
My own Mercury dealer/mechanic told me that Mercury's oil pumps no longer use a motion sensor. This would be true for all the models that have an oil pump, not just certain HP models.

I am unclear what date this change to the oil pump occurred, but it was at least a few years ago.

His impression was Mercury did this because they have high confidence in the oil pump's reliability. My own impression is that perhaps the motion sensor itself was as problematic as the pump, so they just got rid of it.

Newtauk1 posted 09-21-2009 07:26 PM ET (US)
Did the mid-range motors (75-90hp) have problems like the ones being discussed here?
number9 posted 09-21-2009 07:27 PM ET (US)
Per Mercury SM 200/225/250 EFI, starting year 2002.

Oil injection pump is electrically operated and controlled by the ECM.

Pump failure detected by the ECM will result in Guardian system giving continuous sound warning and reducing engine speed to fast idle.

jimh posted 09-22-2009 09:35 AM ET (US)
Thanks to number9 for the information about the substantive change in the nature of the oil mixing pump on Mercury two-cycle engines made after 2002. It sounds like Mercury changed their oil mixing pump from a mechanically operated pump driven by a plastic gear on the crankcase to an electrically operated pump. This is the same solution that is provided as an after-market product:

Marine Solutions (Wisconsin)

They have retrofit kits available for Mercury V6 outboards:

--135 to 200-HP, 1989 through 1999

--200 to 225-HP, 1995 through 2001 3-liter

The manufacturer of this retrofit comes with some credentials. Robert Kachelek, president of Marine Solutions, was formerly the director of Outboard Service for Mercury Marine.

Owners of Mercury motors made prior to 2002 should consider the notion of updating their motors with an electrically operated pump. Given the excellent performance and longevity of Mercury motors, the modest cost of a new oil mixing pump might be a wise investment in preventative maintenance.

toolman posted 09-22-2009 04:22 PM ET (US)
Thanks for the information, but with my engine a 1996 225 EFI with no oil pump rotation sensor it would still not have one with this electric pump upgrade. Is this correct or am I missing something?
number9 posted 09-22-2009 07:21 PM ET (US)

Looked at their info again and appears the kit for your motor includes a speed sensor and oil warning module that should upgrade your warning system.

Denny posted 09-23-2009 08:16 PM ET (US)
Here is some information that may save the owner of a older Mercury engine: I have a 1989 Mercury 100-HP and noticed that I was getting some oil showing up in the well under the engine when I tilted the motor up for towing. After removing the cowling I visually checked the three oil lines. They seemed OK and could not see where the oil was originating from. These oil lines are plastic and about the diameter of a McDonald's straw. Just before I put the cowling back on I touched one oil line, and it came off the distal connection. It turned out that all three connections had the same fatigue symptoms at the point of failure. I suggest that if you have an older Mercury motor that you physically inspect your oil lines because the break is difficult to notice with out moving the oil line.


number9 posted 09-24-2009 12:53 AM ET (US)
Denny--Thanks. That is worth much. And a reminder to do more than just a visual inspection particularly when you suspect or see evidence of a problem.
toolman posted 09-24-2009 04:46 PM ET (US)
With no pump rotation sensor what would be some [symptoms] of the engine running lean or quit oiling before the engine is damaged? Thanks
jimh posted 09-24-2009 09:06 PM ET (US)
As I recall, there has been at least one detailed account already provided in which a Mercury motor with automatic oil mixing was catastrophically damaged from a failure of an oil line, yet no alarm was provided and no warning given.

An alarm system can only detect those conditions which it monitors. Again, there is no sensor that actually monitors oil flow in the Mercury alarm system.

Newtauk1 posted 09-25-2009 01:40 AM ET (US)
Is this a problem with 75/90 hp 2 strokes? Third time I have asked.
Newtauk1 posted 09-25-2009 01:41 AM ET (US)
Yes or No answer.
Denny posted 09-25-2009 06:23 PM ET (US)
You are right. There wasn't a peep out of the alarm system when the oil line was leaking. The only sign was oil in the splash well. The engine would just slow to a full stop. It would start up again and then go to a full stop. Used my kicker to get back in.

I think that if your engine is getting a bit long in the tooth, just replace the oil lines. The replacement doesn't take long at all and all you need if the line, a way to cut the line and some clamps. It is a lot better to do this than look at your motor with a dumb look on your face like I did.

I don't know anything about the other Merc's out there mine is a 100.

jimh posted 09-25-2009 08:48 PM ET (US)
Newtauk1: This is only the first time I am asking you, but exactly what is your question?
Newtauk1 posted 09-25-2009 10:52 PM ET (US)
Sorry about that JimH. I must have asked the questions in another post with regards to the plastic drive gear failure. Perhaps I have confused this thread with the other one.I was asking if the 75hp and 90hp Mercury 2 stokes suffer from the same plastic gear failure.
doubleheader posted 09-26-2009 09:38 AM ET (US)
jim.... thanks for the valued info (someone by this man a cold one!!)

1996 150 saltwater series:
I am having a problem like johnbee was or is :

No alarm at idle, alarm at moderate speed, no alarm at high speed/rpm. (this seems different symptomatically compared to others)
changed water pumps and a gear shaft sensor on the oil pump. after slashing back in the water, ran the boat for a hour and a half... no alarm... got on it yesterday idled for 15 minutes .. no wake zone... went to get up on plane and alarm goes off, so back to idle speed no alarm.. checked everything , looks FINE . go to get back on plane it comes on again.. get up to around 3500 rpm's the alarm shuts off and IS getting oil as we replaced the oil lines with new clear tubing from mercury and you can see it pumping the oil in to the line.

i am leaning to bad module but wanted your 2 cents thanks

gss036 posted 09-26-2009 01:21 PM ET (US)
Without rereading this entire thread, I will add just a little info. If the oil lines get old and crack and allow the oil to run into the lower cowling, there will NOT be an alarm until you have used all the oil the reservoir. Then, it is too late. The little check valve (vent/anti-siphon) on the engine tank will allow oil to run out at times if it it bad. The oil will run out the short hose that hangs on the lower starboard side of the tank. I had that problem on my old Merc and I put a small (4-6 oz) clear plastic bottle at the end of the line and started collecting the oil so I knew for sure where it was coming from.
I have read others stories about the clear hoses cracking and breaking off and the blew their engines for lack of oil.
doubleheader posted 09-26-2009 02:32 PM ET (US)
just got back after swapping out the cap on the ready tank and manually filling up to top, swapping the oil drive gear sensor and grey magnetic cam(yes it is turning) , swapping the oil module, and it is still doing the same thing... no alarm until 1500-1800 rpm idle back down and no alarm.... just for the sake of arguement i placed all componets from this engine on the engine NOT making the alarm and all is good...

next would be a switch box correct???!!!???

doubleheader posted 09-28-2009 08:58 AM ET (US)
when i said all is good i was refering to the parts i swiched over from the motor making the alarm(will label A) to the motor NOT making the alarm (will label B) and installed the parts from the motor B not alarming to the motor making the alarm A and still getting the same results.... 1500-1800 rpm alarm starts to sound... I started motor B with the parts from motor A and no alarm thru rpm range... i am thinking now switch bow any help would be helpful thanks
Tom W Clark posted 09-28-2009 11:34 AM ET (US)
Sure, buy a switch box. The part costs about $250 now.

Even if it turns out that is not the problem, you *will* need the switch box sooner or later, and if later, it will only cost even more.

doubleheader posted 09-28-2009 01:14 PM ET (US)
what else is left to check?????
doubleheader posted 10-11-2009 12:20 PM ET (US)
any body have any ideas??? please help thanks
Tom W Clark posted 10-11-2009 12:34 PM ET (US)
Did you try a new switch box?
doubleheader posted 10-12-2009 12:17 PM ET (US)
no. not yet. was wondering if I was missing something... that seems to be the next step, however that is a lot of wires (to mess up) if it is not the case
doubleup posted 10-20-2009 11:48 PM ET (US)
Motor: 1993 175 mariner. PROBLEM: While setting for a few months oil has gotten into the carbs. The resevoir on the engine is 2/3 empty. Any thoughts as to why it's bleeding out??
jimh posted 10-21-2009 08:25 PM ET (US)
Gasoline left open to the atmosphere will typically evaporate. After two months the gasoline in your carburetors may have evaporated, leaving only the oil behind.
doubleup posted 10-22-2009 11:22 PM ET (US)
Sounds reasonable. However, that doesn't account for losing 2/3 of the upper resevoir. Plus the carbs were full of oil, not just a little excess.
jimh posted 10-23-2009 01:30 AM ET (US)
Check the pressure regulator, which is the fitting in the crankcase that pressurizes the remote oil tank. This component determines how much pressure is created in the remote tank. If there is too much pressure, when the engine shuts off, the pressure in the remote tank will pressurize the whole oil system.

The oil mixing pump has to hold off any oil flow when the engine is not running. If there is a lot of pressure, and if the pump is worn, it is possible the oil could be forced past the mixing pump and on to the carburetors.

One way to test this might be to start the engine, let it run for a few minutes to build up pressure in the remote oil tank, and then shut it off. Wait a few moments, then check the pressure in the remote tank by unthreading the cap. If you detect a lot of pressure bleeding off in the tank, perhaps the crankcase regulator needs to be replaced.

If oil can bleed off from the under-cowling tank just from gravity, without any pressure from the remote tank, then the problem is likely in the mixing pump. It is not holding back oil when the engine is off.

Also see this prior discussion:

Mercury: Oil System: Carburetors Flood With Oil

doubleup posted 10-25-2009 08:27 PM ET (US)
Thanks for the advice. I'll check the pressure and the pump.
elaelap posted 10-26-2009 08:43 AM ET (US)
I think Mercury needs to add a another sensor, the additional one to indicate problems with the primary sensor. I mean, as the Roman poet Juvanel queried, "Quis custodiet ipsos custodes?"


BTW, that roughly translates: "Who will guard the guards?" ;-)

toolman posted 11-25-2011 07:07 PM ET (US)
Jim, I checked the calibration on the oil pump and replaced the vacum valve on the block and my mercury 225 EFI 1996 model engine is still using to much oil. I have checked the consumption 3 times and it is using about 35/40 to 1 . Have you got any idea on what could be causing this and yes it smokes alot on startup. Thanks
L H G posted 12-01-2011 02:24 PM ET (US)
As Mercury oil injection pumps wear out, they introduce too much oil. Sounds like you need a new oil pump.

Servicing dealers have a way to check the amount of oil flow to determine if the pump is worn out. I had one replaced several years ago, and it reduced oil consumption by half.

jimh posted 12-04-2011 10:30 PM ET (US)
Usually when Mercury oil pumps fail they don't pump any oil--the cheap plastic gear stops turning them. Then the engine fails.

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