1992 Yamaha 25hp over heating issues

[Joebeeney]

Here is what I've done so far....
New Impeller and bowl. Cleaned everything around impeller. Never been in salt water. I changed thermostat and blew out the water system from the outlet on back of motor with little to no resistance with an air hose. Motor pees very well but still over heats in neutral at idle after a few minutes.
Note... Old impeller was completely disintigrated when i bought motor and i got all the pieces out of the lower end and water pump area. When i hooked air hose and back flushed the system air came out of exhaust and lower end screens for water intake.

Any ideas.... I'm stumped. Is there any way the head or power head could be clogged if its pumping really well. I also wanted to ad that the water coming out of pee hole is very hot. Burnt my hand.
Motor compression tests at 110 psi as well in both cylinders

[greasyshaft]

I would pop the cylinder head and have a look.
The tell tale is only one of the places that water exits the engine, on Yamaha's the tell tale is usually cold meaning it is expelled from the engine before being circulated around the heads and exhaust.
If there is more resistance to flow up stream(cylinder head etc.) then the pressure downstream(tell tale) can increase

Does the engine overheat when in gear and giving it the berries?

[rodbolt17]

occasionally one must pull the head and ex cover to retrieve impellor pieces.
best way to never do that is to carefully maintain it and NEVER start it dry.