# Outboard overheat alarm



## Evileye (Jan 29, 2006)

Had my impeller changed this spring and was coming into 
wildwood last weekend when the overheat alarm went off. 
Hit the trim button and the alarm went off, I thought I 
picked up some trash. The motor never stopped pissing 
water. This morning I went to launch out of lorain and 
the overheat alarm went off after a couple minutes of 
warming up. I believe its an electrical problem. Anybody 
have any insight into what may cause this?


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## freyedknot (Apr 10, 2004)

does it have a thermostat? what size mota?


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## awe-below-me (Apr 12, 2009)

could be a stuck thermostat, could be a electrical problem... if you have just a dummy alarm, find the bi-metal sensor and pull it out, ground it against the block and see if you get the buzz or beep... mine had gone bad a few years back and i wired in a thermocouple instead, and added a real gage to my dash. now its never a question on what the temp is.


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## Evileye (Jan 29, 2006)

Its a 90 hp Mercury


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## freyedknot (Apr 10, 2004)

http://forums.iboats.com/showthread.php?t=127860


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## Whaler (Nov 16, 2004)

Check with C.J.Stone . I think he ran into this awhile back.


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## Evileye (Jan 29, 2006)

Thank you. I believe its the temp sensor after doing a little research
myself.


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## crappiewacka (Apr 7, 2009)

I ran into this a while back on my '91 60 hp. Merc. After I changed the impeller, oil injection line (which was cracked) and checked oil sensor, the alarm sounded again. It was the thermostat. Then after a couple outings, damn thing went off again as I was putting around looking for structure! So please post back if you figure it out!! *PLEASE!!!*


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## Evileye (Jan 29, 2006)

It was the electronic warning horn module. 120.00 worth. They also
checked temp and oil senders and for shorts under the dash. Hope this helps
somebody.


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## OHBMQUINN (Sep 11, 2007)

Sometimes the warning buzzer can mean lots of things like water in the fule low oil level wich can be caused by a bad bypass valve or oil level sensor or over heat oviously


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## Carpn (Apr 5, 2004)

Just because your motor is pumping water good doesn't mean it isn't overheating. I had a T stat go bad this spring while in LA. I orginially though it was bacause of a blockage cause we were in shallow weedy water. I would pull the indicator and stick my finger in the outlet hole and let it build pressure then realease it. It cleared it out eh first few time. The last time it wouyldn't clear. I'd just replaced my impellar but when I pulled the cover on the engine it was obviously hot on the top side of one of the cylinder banks. I ended up pulling the plug wires off the last plug on that side and it let it run cool enough for me to get on plan and head back to the ramp at 12am. The next morning I replaced both Tstats as well as the temps sensor because it had gotten hot enough that the plastic thread on the sensor had melted and it had pushed out of the thermowell.Now I carry a extra tstat as well as extra plugs...


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