1989 80HP outboard Merc - High Temp Alarm after 30min of use

[xaser]

I have a 1989 80hp merc on the back of my 16' Doral.

After running the engine and boating for about half hour the high temp alarm comes on. I've had two boat mechanics take a look at is and still can't figure it out.

This is what has been done so far.

-Stater changed
-High Temp Sensor changed
-Modual changed
-water pump and impeller still good
-Thermostat changed

All this could rack up in price but lucky me I don't need to pay for the parts until the problem has been resolved.

I know the problem isnt weeds around the prop, When I take the cover off the engine it does not appear to be overly hot and the Engine Runs amazing, not sluggish by any means with tones of power for what it is.

When the alarm comes on I can turn the key slightly to the off position without shutting down the motor and the alarm will turn off but so will my gas gauge. I only do that as a temp measure because the noise becomes annoying.

Any help

 

[xaser]

Maybe its the high temp buzzer shorting out? Sometimes it comes on when I go over waves or rock the boat. Sometimes the alarm comes on and stays on when the motor isnt even started

 

[haventaclue]

I think you have a wire shorting out somewhere.Trace the temp wire,look for broken insulation

 

[fastjeff]

It could simply be the temp sensor itself. I suggest checking it out with an inrared temp gage.

Jeff

 

[xaser]

It could simply be the temp sensor itself. I suggest checking it out with an inrared temp gage.

Jeff

But if it was the high temp sensor why would it beep as soon as I turn the key without even starting the motor?

 

[racerone]

If this is a control box where you normally get a single " beep " when you turn the key on with a cold motor , then you might have a defective buzzer.