Need a Genius to Solve my Overheat Problem

1998 90hp inshore series. At idle for too long, the engine overheats and alarm goes on and engine goes into protection mode. If running at high speed, will go a while longer, but still eventually gets too hot. I think the pistons are staying cool enough to not overheat the engine, but I think the head cover is getting too hot, and setting the switch off. I have a thermostat to the head cover, and goes well past 175F when it gets hot. (Also, I have removed the switch so it just hangs in the air so engine does not shut off, and run the engine hard.....head cover gets way too hot But no seizing.....again I think pistons are staying cool enough but head cover gets too hot)

I have put a new pump in. I have put a new thermostat, pressure spring, and thermo switch. I took the head cover, head and exhaust plates off. Cleaned out all deposits and looked for blockages. NOTHING!!!!! I have no idea what else I could possibly check.

Nobody can solve this problem. Can you??

[boats.net]

If haven't replaced entire water pump do so, next would be to remove powerhead and check water tube and rubber grommet.

yeah....I agree that may have to be my next step. I must have a partial block between the power head and pump. Removing the power head to get to it.......sounds like a MAJOR project. Is it? How do I go about that?

[boats.net]

It's not bad unless it has saltwater corrosion.

What kind of water pressure numbers are you seeing at idle, mid, & wide open throttle? Do you always have a solid stream of water coming out of the pee hole?

Any chance the water pump prop was installed backwards? When did this issue begin? Was there any particular event that you can recall that might have triggered the issue?

-Rich
Austin, TX