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Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10662
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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Turn ignition key to on position and warning horn beeps continuously

Customer Question

Turn ignition key to on position and warning horn beeps continuously with engine running and without engine running. Ran test on overheat sensor and it test fine. Not sure what to test next?
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.
Hello. Did you test both over heat sensors? Could I get the engine serial number please?
Customer: replied 1 year ago.
0T076858
Yes, both have been tested. Everything was operating fine yesterday and today starts as soon as I turn key on; engine does even have to be on and horn sounds continuously.
Expert:  Tan replied 1 year ago.
Locate the oil sensor in the top of the oil reservoir and test it with an ohm meter. You should have no continuity. Do you have continuity?
Customer: replied 1 year ago.
It test OK. I just replaced the oil tank and sending unit. Haven't even had the boat on the water since tank was changed out.
Expert:  Tan replied 1 year ago.
Disconnect all the sensors temp and oil does the alarm quit?
Customer: replied 1 year ago.

Went out this morning and horn functions properly now and does not beep continuously. Ran engine for few minutes now it's running rough and rich. I oil sensor tested OK (no continuity). I retested Temp sensor today with ice water test and the continuity changed inversely with temperature change, so I assume the temp sensor is OK. By the way the oil sending unit and tank are brand new, just installed several weeks ago due to a leak,

If you remember, I'm the one with the vacuum hose issue pertaining to MAP Sensor. I switched the hoses out the other day and the engine ran fine. Today is another story.

Expert:  Tan replied 1 year ago.
Hi Gary. Yes now I remember. This would indicate the MAP sensor is going out as it will cause a weird alarm issue and run rough. Since we have eliminated the other sensors that leaves the MAP sensor or the ECM. Being as it is intermittent I would replace the MAP sensor.

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