Tranny causing my overheating?

[tuffenuff]

Last season my '88 Prostar had a strange overheating issue. Temp. gauge would peg hot, then drop into normal range within seconds. If I was idling and it did this I would throttle up and it would cool down. Just the opposite if I was into the throttle, I would drop the idle and it would cool down. Thermostat, temp. sensor impeller, etc. were all changed. All hoses from the raw water pick-up to the exhaust pipes have great flow. The closed cooling system is also flowing well. Some on this site said that I might have a tranny cooling issue. Today I removed and inspected the heat exchanger for the tranny. Flow is good. Does my boat have a strainer or filter pertaining to the tranny lines that I can't find? Any insight from those who know the answer to my question would be greatly appreciated. Thanx in advance. Scott

[88 PS190]

The transmission doesn't really have anything special, from the through hull fitting there is a hose to the strainer, from the strainer to the raw water pump, from raw water to the engine.

There are no extra filters hanging out for the transmission.

I do not see the transmission causing your engine to overheat. But you could have bits of the old impeller in cooling passages, electrical issues giving you false readings etc.