Is there a way to test Mercury outboard overheat alarm with a pan of hot water?

Bumblebeeman9

Recruit
Joined
Apr 8, 2020
Messages
2
I'm concerned that somewhere in the overheat sensing system, either the sensor itself or the wiring, that something is not working. It's definitely not the horn itself because if I put 12 V on the horn it beeps. It's my understanding that if you short the tan wire connection at the bottom right of the engine to ground the horn should go off if everything is good. When I put a double-sided alligator clip from the tan wire connection and touch it to a cylinder head bolt with no paint on it the horn does not beep. So my first question is:

Should the horn beep if I touch the bottom right tan wire connection to a cylinder head bolt with no paint?

If I connect the tan wire connection to the upper of the 2 little terminal connections about 5 inches aft of the starter motor the horn sounds. But I'm afraid that's just completing a connection that gives 12 V straight to the horn and doesn't indicate the wiring to the cylinder head temperature sensor is correct.

Is there a way the cylinder head temperature sensor can be disconnected from the head and put into a pan of hot water to test its proper function and the wiring? If so what temperature water should I use? And is it the sensor from the left side cylinder head or right side facing forward?

Thank you
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,937
Ok ...First key has to be in on position for overheat horn to work. The tan is nothing but a ground when sensor closes. If you take your clips and attach to engine bolt and tan wire from engine side harness(not sensor) it should be a constant beeeeep as long as you hold the wiris together. If no horn wiring harness problem. Yes you can test sensor in water with ohm meter..
It's my understanding that if you short the tan wire connection at the bottom right of the engine to ground the horn should go off if everything is good. When I put a double-sided alligator clip from the tan wire connection and touch it to a cylinder head bolt with no paint on it the horn does not beep.
This wire location you are describing is for a temp gauge not horn..
If I connect the tan wire connection to the upper of the 2 little terminal connections about 5 inches aft of the starter motor the horn sounds
This is correct operation...
 
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