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Over temp alarm

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pollard1944

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I have a 1996 115hp Johnson outboard model # J115GLEDR. The water pressure gauge reads around 10 at idle and climbs to over 30 as the rpm increases. Compression on all cylinders is around 120. I have had the water pump and thermostats replaced, but I still get an overtemp alarm after running at high rpms for a few minutes. I found a small amount of water on one of the spark plugs when doing the compression test.
 
That small amount of water may be due to a failing head gasket. That would also allow the combustion power of the cylinder to slip past the gasket and enter the water jacket area. If so, this results in stalemate of sorts...... the water rises up the water passages, runs into the combustion power and can go no further which results in a overheating scenario.
 
That mtr is a 60* v-4 and has no head gaskets, just o-rings. Does this mtr go into SLOW when the horn blows? First thing I'd do is verify it's overheating with an infared temp gun as you may have a bad horn.
 
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I've got a 97 Johnson 115 Fast strike and have the same problem. I've searched the web and have seen this problem many times in post but no one ever tells how they fixed it. I bought my motor brand new in 96 and had no problems until it started this alarm and sometimes going into slow. I took it back to the dealer under warranty and it was so intermitten they couldn't find what was wrong. Back to present day, it set in storage for 10 years. I got it out 2 years ago and ran it with no problems except the alarm going off all the time again. I have the system check gauge so I know it's a water temp alarm. Whenever the alarm goes off I can put my hand on the head and keep it on with only feeling a little heat. If it was truly overheating I would of already melted it to the ground. The year I got it out of storage I ran the entire length of KY lake from Pickwick Dam to KY dam 184 miles with the alarm going off ever so often and I would stop and check the motor see it wasn't hot and continue on. I checked the water pump impeler and it looks like new. The termastats seem to work. The sensors, When the alarm goes off I can unplug both sensors and the light still won't go off. I wish it was a way to just bypass all the system check but would like to fix it if I can.
 
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