mercury warning horn

[turkeycreektrout]

hello
i have an 89 mercury 80 horse oil injected on a skeeter bass boat.
the motor runs fine, but the other day the horn came on and stayed on for like 4 minutes then went off. i believe a horn comes on until the thermostat has reached full temp, but we had the boat running when it came on.
can someone tell me what warning horns mean what on this particular motor?
thanks
sean

 

[turkeycreektrout]

Re: mercury warning horn

well i just found out by reading that it means the engine is overheating. what could cause this? the water pump is working and there is water shooting out of the engine. the person i bought the boat from replaced the thermostat and he said that the horn sounds until the temp reaches something like 144 degrees.

the motor itself runs fine
any advice would be greatly appreciated
sean

 

[j_martin]

Re: mercury warning horn

I ran over a floating rotten log once, cut it clean in half. Alarm went off and water pressure went to about 25 lbs.

Took quite a bit to get all the wood chips out of the cooling system and base plate.

Did it once with a big gob of floating algae, tool. Not quite so hard to clean up.

It could be a simple as tired insulation on the wire to the sensor in the head shorting to ground. It could also be a fault oil alert module. The two circuits come together at a screw either on the switchbox mounting plate, or just over it. There you can isolate the problem.

hope it helps
John