overheating alarm

[bioalan45]

I have twin 1993 150 hp Yamaha outboards. My "engine overheating" alarm goes off occasionally but the motor is not overheating. The mechanic has replaced the thermostats and the 2 sensors that send the signal for the alarm. Nothing has helped. Any ideas. This does not happen every time I go out. Someone said it could be the CDI storing a bad code and from time to time setting off the alarm. Help.

[boats.net]

Temp of engine needs to checked at time the alarm is going off on both cyl heads.

[ausnoelm]

Do you find it only happens when running at higher RPM for a while?

[99yam40]

If the temp sencers are functioning properly then you could have a hot spot around the sencer due to cooling passage blockage or your PRV is dumping too much water at low RPM because it is stuck open if that is when the alarm is coming in