I have twin 250 Yamaha 4 strokes on my boat and recently the overheating alarm has been going off on the portside engine while trolling or at idle speed. I can turn the engine off an back on and the alarm will stop for a minute or so but then will reactivate once again. I changed the waterpumps and thermostats out on both engines in hopes that my problem would be corrected however that has not been the case and now the alarms on both the port and starboard engine is going off at low idle speeds. I know the alarm is controlled by a sensor on the front of the motor but was not sure if the sensor is actually my problem or if the problem could be coming from a blockage somewhere that is restricting the water being passed through the engine. I am new to the forum and would greatly appreciate any advice.