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Author Topic:   Optimax oil warning horn
Royboy posted 05-21-2007 08:42 PM ET (US)   Profile for Royboy   Send Email to Royboy  
Maybe coincedence, but I added DFI oil for the first time this year and now I'm getting an oil warning tone and light. I removed and cleaned both caps on the tank and checked to make sure there was oil in the under-cowl tank, and there was (about 3/4 full). I then ran the engine on muffs for a good ten minutes with no horn. I also removed the cap on the under-cowl tank while it was running but it didn't seem to change anything.

I Launched the boat today to go fishing and it didn't run for two minutes and the horn went off. The engine is running fine but this stupid horn is driving me crazy! What should I check?

Royboy posted 05-21-2007 09:08 PM ET (US)     Profile for Royboy  Send Email to Royboy     
O.K., so I panicked a little. There is a splendid troubleshooting chart on page 3C-16 of the Mercury Service Manual. I'll follow the proceedures outlined see where we are then.


wayne baker posted 05-21-2007 10:12 PM ET (US)     Profile for wayne baker  Send Email to wayne baker     
I wish you better luck than I had. My 1997 175 offshore just striped a gear on the oil pump. What would have been a 1200.00 dollar repair. For 175.00 will pick my boat up tomorrow and pour oil in with the gas from now on.
jimh posted 05-22-2007 01:15 AM ET (US)     Profile for jimh  Send Email to jimh     
The plastic drive gear certainly is the weak link in the Mercury oil system. I do not recall a single instance where anyone has reported making a repair when this happens due to the very high cost.

An alternative to pre-mixing the oil and gasoline is available. 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.

Royboy posted 05-22-2007 07:40 AM ET (US)     Profile for Royboy  Send Email to Royboy     
Perhaps I should elaborate on what I mean by, "the engine is running fine". I ran out to my fishing grounds on Lake Erie (12 Miles) at 5000 rpm and 40 MPH and then trolled for four hours. Two days later I did the same thing, except it was rough and I kept it at 3000 rpm and around 21 MPH for the 12 miles, and then I trolled for six hours. The horn was sounding the entire time every two minutes per specification.

I do not think it is a stripped gear.


wayne baker posted 05-22-2007 09:22 AM ET (US)     Profile for wayne baker  Send Email to wayne baker     
Jim thanks for the info. I will look into it.

Roy, Good luck with the alarm. Don't wait too long to find out what is going on.If it is not a faulty alarm you are killing your motor. By the way My alarm stoped too when there was no load on the motor at the dock. I put mine on the trailer, I would not chance going out.

Royboy posted 05-22-2007 05:10 PM ET (US)     Profile for Royboy  Send Email to Royboy     
O.K., so we could change the title of this thread to: "Mercury Optimax Low Oil Warning System Works as Advertised". I took the cowl off this morning and the oil level on the engine tank was much lower than yesterday. I filled it by siphoning some out of the remote tank. Oil siphons extremely slow by the way.

After filling the tank, I thought it would be a good idea to purge the oil system per the service manual instructions. Basically, this involves pumping the fuel primer bulb, then turning the key to the "ON" position and withing ten seconds, moving the shift lever from "Nuetral" to "Forward" 3 to 5 times. The oil system then primes itself and puts the engine into the 120 minute break-in mode.

After this completed (about three minutes later), I started the engine on the muffs and loosened the plug on the engine oil tank to purge all of the air out of it. This time it worked as it should. I secured the cap and then checked for oil leaks with a powerful flashlight and an inspection mirror. I didn't find any. The engine ran for a full fifteen minutes with no oil alarm. When I have the problem, it would sound almost immediately, likely within the 25 second spec, although I wasn't timing it.

I beleive what happened is this: When I filled my remote tank I didn't get a good seal on the fill cap. With air leaking from the tank there was not sufficient pressure to keep up with the oil demand of the engine, and the engine tank eventually ran below the level where the alarm is triggered. By the way, there is a sticker on the remote tank that says: "the caps must be tight!" I guess they mean it.

No harm done, and I got to learn a few things about my engine's oil system. Nice to know that it works as it should.


bsmotril posted 05-22-2007 11:15 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
There is a very fine mesh filter screen in the pickup tube inside the remote oil tank. Over time, it will form a sludgy coating that will clog the mesh and restrict oil flow to the engine mounted tank, which will then run low. You should remove the cap on the remote tank that contains the pickup tube, and clean it anually.
jimh posted 05-23-2007 12:02 AM ET (US)     Profile for jimh  Send Email to jimh     
Roy--Thanks for the nice description of the instruction manual procedures. I love instruction manuals, and it is good to hear that the Mercury instruction manual has all of that information in it. So many owners never thoroughly read the instruction manuals. I force myself to review things like the recommended starting procedure so I do not get into bad habits.
Royboy posted 05-23-2007 07:36 AM ET (US)     Profile for Royboy  Send Email to Royboy     
I did check the screen by removing the pickup tube form the cap, draining the oil from it and then blowing through it. There was no resistance.

I too was impressed with the Mercury Service Manual this time, although at times I have found the maintenance descriptions somewhat cryptic. The troubleshooting chart for the oil system, however is outstanding. There is also an superb description of the oil system in general, including the warning functions. I'm also a big fan of Service Manuals, having spent ten years as an aircraft mechanic in the USAF where their use carries the weight of lawful orders. I grew fond of a well executed repair manual, and the Technical Orders of the USAF are second to none.

So far have used the Mercury Service Manual to change an impeller, and to troubleshoot a low oil warning alarm. Even with it's shortcomings, I have to say that it has saved me many times its purchase price.

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