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Author Topic:   Mercury BEEEEEEEEP Continuous Alarm
jwalker290 posted 08-25-2009 10:56 AM ET (US)   Profile for jwalker290   Send Email to jwalker290  
I have a 2004 Mercury 200-HP EFI Saltwater edition outboard. Recently, the continous tone or horn starting blaring [when the motor is running at about] 1,200-RPM, after returning back from about 45 minutes of higher speed running, 4,000-RPM. I immediately checked the water pump stream, and it is good and strong. I assumed [the alarm sounding was to indicate] the low oil warning, and shut the engine off. I was only about a minute from the dock, so started it up again, horn blazing, and got back to dock.

Per the owner's manual, I checked to make sure the remote oil tank caps were tight; they were. I removed the engine cowling to visually inspect the engine oil reservoir level. It seemed to only be down about 3/8-inch, but I followed the instructions on removing the cap and running the engine to bleed the air out. That only took about five seconds for oil to come out of the top, so I secured the cap, and ran the engine at idle for about five minutes with no alarm.

Besides checking the obvious, loose cap at oil tank, loose hoses on all the oil system lines, is there any other things I can do to troubleshoot? What would cause the oil level in the engine reservoir to be low? and would a 3/8-inch drop in oil level be enough to trigger the alarm? Could the pick up be clogged a bit? I have not removed the cap on the oil tank where the two lines come it to inspect that.

Thank you iin advance for any suggestions.

wbullwin posted 08-25-2009 03:10 PM ET (US)     Profile for wbullwin  Send Email to wbullwin     
I'm not sure I can help since I do not have an engine like yours but I do have a 90 HP with an oil tank under the cowling. If I read your posting correctly, you say you ran the engine for 45 minutes at 4000 RPM and the oil ONLY went down 3/8". That doesn't sound like very much oil for that size engine. Then you said after you put the cap back on when trying to bleed it, it ran for 5 minutes without the alarm sounding. That sounds like it is fixed. Maybe you had a vapor lock and the oil couldn't get out and that set off the alarm. I'm not an expert, just throwing out some suggestions. I would be concerned about the lack of oil though.
jwalker290 posted 08-25-2009 04:23 PM ET (US)     Profile for jwalker290  Send Email to jwalker290     
Sorry, should have been more specific...I meant that the powerhead oil reservoir was only down 3/8-inch from top. The large remote oil tank has been drawing down, but not as much as it seemed to before, but I cannot say that for sure, I have not measured that closely does appear lower.
Buckda posted 08-25-2009 04:34 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Hopefully we'll get some Mercury experts to weigh in here.

Do you have a strong understanding of how the oiling system works on your motor? Is it possible that the prolonged WOT operation is using a higher ratio of oil out of the powerhead tank, and when you slow down, the flow from the remote tank is slowed, before or "out of sync" to when the flow from the powerhead tank slows? I.e. it could continue to oil at a greater volume ratio for a few minutes after you slow down, but the tank is not replenished from the remote tank quickly enough, resulting in the alarm? I'm thinking that it may be a stuck or sticking part, or even a slight pressure leak somewhere that is causing a discrepancy after prolonged high-RPM use.

L H G posted 08-25-2009 07:39 PM ET (US)     Profile for L H G    
You've been falling all the Mercury EFI oil injection baloney being circulated around this site. A continuous horn means engine overheat, NOT OIL INJECTION.

Take it to a dealer for service. Water pump could be improperly installed, poppet valve, thermostat promblem, or a defective temp sensor on the engine (which happened to me).

rtk posted 08-25-2009 08:53 PM ET (US)     Profile for rtk  Send Email to rtk     
First- welcome to the site!

Larry knows these engines and Mercury systems like the back of his hand so I am making my comments assuming that you are getting an overheat alarm and not an oil alarm.

Sounds like you picked up something in the water while running that blocked the raw water intake causing the engine to overheat and sound the alarm. Upon restart the engine temperature was still high enough and remained high enough on your 1 minute return to the dock to trigger the alarm. I say this because you said you ran the engine for about five minutes while bleeding the oil system and you did not get an alarm during that time. The engine may have cooled down enough so the alarm no longer was activated.

Running an engine until it sounds an overheat alarm to diagnose a problem is a bit dicey but you may want to give it another go under load before taking it to a dealer.

If the engine alarm sounds and I have a strong stream of water showing I typically will lightly touch the top of each cylinder head with my palm for a very short period of time to see if the heads are excessively hot. If you can tolerate the temperature on your skin it is probably not overheating. A more precise way to check temperature would be to buy an infrared temperature sensor and measure each cylinder head temperature. My 2003 Mercury 250 EFI only runs at about 120 degrees under normal operating conditions.

If temperature at the cylinder head is normal and the temperature alarm is still sounding then there may be a fault in the alarm system. You will need a manual to work your way through the electrical system of the alarm system to troubleshoot the problem.

If the engine is running hot and the confidence stream is strong I would first look at the thermostats. If they have not been changed in 5 years and you run in a saltwater enviroment they may be shot. I like to change mine after 3 years as a maintenance practice running in saltwater. If they are not visibly all crusty and rusted you can test them in hot water to see if they open and close. Boil some water on the stove, dip them in and see if they open and close.

Hope this helps- good luck with the problem.


jimh posted 08-25-2009 11:18 PM ET (US)     Profile for jimh  Send Email to jimh     
I think L H G is referring to the dozens of articles posted by owners of Mercury motors on this website about problems with their oil systems and alarm systems. These are extremely common topics here, and it is because they are extremely common problems with Mercury motors.

Getting back to your alarm sounding and how to interpret it: there is no way to interpret the cause of the alarm on a Mercury outboard other than by the cadence of the alarm and the circumstances when it occurs. The operator has to interpret the meaning. Generally a continuous alarm comes from the temperature sensor. About the only way to determine this with certainty is to disconnect the temperature sensor and see if that quiets the alarm.

In any alarm system, when the alarm sounds there are three possibilities:

--there is an alarm condition, a sensor has detected it, and the alarm is properly sounding, or;

--there is no alarm condition, a sensor has malfunctioned, and the alarm is sounding but it is a false alarm, or;

--there is no alarm condition, no sensor has malfunction, the alarm itself or the electronics that control it have malfunctioned, and there is a false alarm.

You have to investigate these three possibilities. It is best to assume there is an alarm and proceed accordingly with caution about running the motor.

In the case of a continuous alarm tone, locate the temperature sensor. The temperature sensor will usually be located on the cylinder block, typically near an upper cylinder. It typically will have a brown wire. Disconnect the sensor from the brown wire--usually there is a connector or plug. IF this stops the alarm, then the alarm is coming from this sensor.

Now you need to determine if there really is an over temperature condition. Measure the cylinder head temperature with another thermometer. An infrared thermometer is handy for this. If the cylinder head is too hot, the alarm was valid. Investigate the cooling system.

By the way, the cooling system on Mercury motors often needs annual maintenance of the rubber impeller. Mercury cooling systems also need frequent maintenance of their thermostats and poppet valves. It is very likely your alarm is a valid over-temperature alarm and you have a malfunction in the cooling system. There are many reports of this problem. I know someone with Mercury motors and they have very frequent service on their water pumps in order to maintain the cooling system.

If the alarm is coming from the temperature sensor, and there is not a high temperature condition, then the sensor is bad. The usual technique is to remove the sensor, heat it in a pan of water with a thermometer, and see when it closes the circuit.

If the alarm is not coming from the temperature sensor, leave the temperature sensor disconnected and look for other sensors. There is a sensor for the oil level in the under-cowling tank. Check that sensor by disconnecting it.

There is also a sensor for the oil pump. Disconnect that one, too.

If you get all the sensors disconnected and you still have an alarm, the alarm module may be bad. This is a very frequent condition. Of three people I know with Mercury motors, all three have had failures of their alarm module and had to replace it. Again, a common problem.

Finally, see the REFERENCE article on the oil system for a better understanding of how it works:

L H G posted 08-26-2009 01:17 AM ET (US)     Profile for L H G    
The problem with Jwalker's engine is simply a defective overheat alarm. If the engine was truly overheated, he would have known it, and the hot engine would not have re-started as he indicates.

The oil injection system on the 2004 Merc EFI's is much more sophisticated than the early 1989 system Jim has detailed. It does not apply to a 2004 engine.

jwalker290 posted 08-26-2009 08:14 AM ET (US)     Profile for jwalker290  Send Email to jwalker290     
Thank you all for your responses. I appreciate it. This engine is always run in salt water, has about 150 hours since new, and I have not had the water impeller changed, or any other service for that matter, except for new plugs every year. I've put about 110 of the 150 hours on it, always fresh water flush it after every use, but was wondering what the useful life of the impeller was.

I guess it's time for me to take it for service. Should I just bite the bullet and have them change out the thermostat, impeller, etc? or let them diagnose and come to their own conclusion?

Thanks again to all that responded!


newt posted 08-26-2009 12:38 PM ET (US)     Profile for newt  Send Email to newt     
Since your engine is 5 years old and you don't know that the water pump has ever been serviced, and you are having overheat problems, then yes, have your mechanic do the service.
jimh posted 08-27-2009 09:33 AM ET (US)     Profile for jimh  Send Email to jimh     
"The oil injection system on the 2004 Merc EFI's is much more sophisticated than the early 1989 system...."

It was reported recently that the newer engines lack the motion sensor on the input shaft to the oil mixing pump as part of the alarm system. Is deletion of that sensor what is meant by "much more sophisticated"?

An thorough explanation of the new features of the Mercury oil mixing system would be a welcome addition.

number9 posted 08-27-2009 10:22 AM ET (US)     Profile for number9  Send Email to number9     
My little 1987 70s don't have the motion sensor either. They must have incorporated it later.

Is it possible on some of the newer ones without that sensor they changed to a metal gear?

bluewaterpirate posted 08-27-2009 11:04 AM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
I change out my OPTI water pump impeller every 300 - 400 hours (because I run exclusively in deeper water) never had any issues with themostats etc. If you run your motor in shallow water and pick up sand and brackish debris then I would recommend changing your impeller every 150 - 200 hours.

My Opti cooling system has been rock solid.

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