Motor is an '82 Evinrude 55hp. I dropped the lower unit and changed out the oil and water pump, and replaced top end thermostat. Changed plugs and borescoped the inside of cylinders with pleasant results. It still ran for about 3 minutes at idle and I would get the overheat buzzer. Remembering that the temp sensor is an RTE (remote temperature sensing element) that increases resistance with temperature, I traced the wiring and found a well hidden hack job under some heat-shrink that showed significant wiring deterioration. This caused higher restistance in the wire and gave me the bogus alarm (remembering, higher resistance= higher temp as far as the alarming circuit is concerned). Of course, if your high temp buzzer goes off, first make sure your motor is pumping cooling water, thermostat works, fuel mix isn't outta whack, and flow isn't clogged. If you've chased all that down, then check those wires! Too many ohms = too much alarmin'. Check it all out but don't forget the wires. Shoulda ran an ohmmeter check on the wire between the buzzer and sensor earlier...but then again, water pump and thermostat replacement is a good idea from time to time.
