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Author Topic:   Mercury Warning Horn Reset
wayne baker posted 02-25-2008 10:46 AM ET (US)   Profile for wayne baker   Send Email to wayne baker  
I just hooked up a [Mercury outboard motor warning] horn to my [Mercury outboard motor] wiring harness. The wires looked as if the horn had been removed in a bit of a rush. As suspected, when the ignition key is switch on the warning horn continues to beep in one second. Is there anything I could look at quickly? I am thinking like a loose connection, as the motor is not running. There is heat or oil problem.
wayne baker posted 02-25-2008 11:52 AM ET (US)     Profile for wayne baker  Send Email to wayne baker     
After tracing some wires back to the motor I believe the problem is an electrical junction box for the temperature and oil alarms. I think I need a professional to check it out for me.
Tohsgib posted 02-25-2008 12:21 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Temp and no oil alarm is steady, low oil alarm is intermittent. Pull low oil alarm sensor or replace it. Oil alarms in my opinion are BS. You know to keep it full and if your pump does quit by the time that alarm goes off you probably stuffed a piston anyway.
Tohsgib posted 02-25-2008 12:22 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
PS on Mercs I think the VRO pump might be going south if alarm is going off as well. Might be time to disconnect and start premixing depending on year and size of engine.
wayne baker posted 02-25-2008 01:00 PM ET (US)     Profile for wayne baker  Send Email to wayne baker     
I am fairly sure that oil is steady on alarm and temp is a fast beep. My last mercury the oil pump quit. Because of the alarm I dumped a gallon of oil in the tank and idled back to the boat ramp. Thanks to the warning horn I did not damage the engine. The warning horn saved my last engine so I would really like to have it working on this engine
Tohsgib posted 02-25-2008 01:05 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Well then Mercury is opposite of all other brands I have owned. Maybe why I never owned Mercs.
an86carrera posted 02-25-2008 07:12 PM ET (US)     Profile for an86carrera  Send Email to an86carrera     
Low oil on a merc could be either 'low oil' or 'no oil' depending on year and HP.

Where is Larry when you need him?


Tohsgib posted 02-25-2008 07:18 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Last I heard he was out in Miami counting all the Verado engines VS E-Tecs ;)
wayne baker posted 02-25-2008 09:13 PM ET (US)     Profile for wayne baker  Send Email to wayne baker     
My motor is a 1994 Mercury 100-HP. It has an [oil] reservoir under the [engine cowling]. I filled it up just to make sure that was not the problem. Again I think this is ouside my shade tree skills. I am going to have someone check it out.
bill705 posted 02-25-2008 10:42 PM ET (US)     Profile for bill705  Send Email to bill705     
I've got a 1991 100hp and the one second beeps are caused by the low oil switch. It's at the very bottom of the tank and has two wires coming from it. You could disconnect one via the quick disconnects to see if that is what is causing it.

Or you could take out the one screw that holds it in and drop it down out of the tank. It's in a blind hole so no oil will come out when you do.

There's a little ring magnet attached to a round float that's inside the tank and the magnet came off of the float on mine. Only fix is to replace the tank. If it's been sitting for a time with no oil in the tank I guess it could stick to the bottom of the tube if the oil sort of gummed up.

What ever you do be sure to check all of the oil lines after you've fooled around in that area because they really get brittle and break very easy.

jimh posted 02-26-2008 12:05 AM ET (US)     Profile for jimh  Send Email to jimh     
The outboard motor's owner's manual ought to give you some guidance on how to interpret the alarm horn's cadence to figure out what it is trying to say. These primitive alarm systems rely on the operator to deduce the meaning of the alarm by either interpreting the cadence of the alarm signal or by interpreting the circumstances in which the alarm occurs. The Mercury alarm horn and the alarm circuit that drives it seem to be components that commonly fail. Try searching for the terms "Mercury" and "BEEP BEEP BEEP" and you find many prior reports. Here is a link: BEEP+BEEP%22

In the REFERENCE section there is a good article on the Mercury oil system. See:

That article says:

"If warning horn should sound an intermittent BEEP BEEP BEEP during operation, this indicates a problem occured in the oil injection system."

To read about the float magnet, try: magnet

Tohsgib posted 02-26-2008 11:08 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
On a 100hp...just disconnect and pre-mix. You will get peace of mind that it CAN'T fail and the extra oil per year will be about $20.
wayne baker posted 02-26-2008 07:20 PM ET (US)     Profile for wayne baker  Send Email to wayne baker     
Good info bill and Jim. Thanks for the help I will be all over that tomorrow. I may go the disconnect route but I would really like to know for sure what is going on first. I see smoke and the water is not hot out of the pisser(is it ok to call it that) so I know it is just a bug, so to speak.
David1877 posted 03-04-2008 01:33 AM ET (US)     Profile for David1877  Send Email to David1877     
I have a 2005 Optimax 200. The first day I ran it the oil horn came on.

I later found out the oil lines were installed incorrectly at Twin Cities or Whaler, but before I figured that out, I learned a few things about the little reservoir under the cowling.

I presume your engine is an oil injected 2 stroke.

The oil tank on the engine is a reserve tank. When oil gets low, you get an alarm before you run out of oil.

In may case, I refilled it. The alarm stopped, and restarted a few moments later.

Presuming your system is corected properly, check to ensure the oil caps are on tight and secure and that the hoses are ok.

If you had to manually fill it and you have plenty of oil in the oil tank/system, it might be that your oil system is not pressurized correctly.

My owners manual states: IMPORTANT: Always make sure the oil tank caps are threaded on tight. An air leak will prevent oil flow to the engine.

Here is the fix:

Tilt your engine so the onboard tank is level. Remove the little cap on the oil reservoir. Run the engine until the tank fills with oil to overflow. When the air is pushed out by circulating oil, replcae the cap on the oil reservoir under the cowling. Stop the engine.

This will get the air out of your oil system and it might cure your problem.

Good luck,


David1877 posted 03-04-2008 01:39 AM ET (US)     Profile for David1877  Send Email to David1877     
Presuming your system is corected properly...

Sorry..I meant connected properly

wayne baker posted 03-05-2008 10:54 AM ET (US)     Profile for wayne baker  Send Email to wayne baker     
Looks like it is the level switch I replaced the module and (I think I damaged it messing with wires). Now with one wire unplugged on the wires going to the bottom of the tank I get an ok beep when I turn the switch to the on position. Thanks for all your help

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