1993 200hp Might be the end

I bought this along with a 25ft Proline and it ran well for 6 months. I started getting an overheat alarm at full throttle and took it in to the dealer for repair. He said one head is getting up to 200 degrees and the other 180. He replaced the thermostats but that did not help. I replaced the impeller last year and its pumping plenty of water. His feeling is the innards are clogged with salt corrosion and the cost to tear it apart to clean it out exceeds the value of the engine. I also replaced one head last year and I know it to be a super clean freshwater part.

I certainly don't want to undertake the task of tearing it apart either. Anyone else ever been in my predicament? Seems a shame, if I keep it under 4600 rpm its OK, it doesn't overheat, but I don't trust it enough to take it far.

2 stroke ?-----Head gaskets are cheap if you want to have a peak at the water passages.----And don't forget to inspect passage way of water intake in the lower unit.

The repair shop give you the old parts?
The condition of the thermo's can be an indicator of the condition of the cooling passages.

When I work on an overheat: I use a heat gun and gauge the temp on all areas of the block.
Early 90's 40hp Yam that was running hot.
The thermo was clogged completely and the cooling passages were blocked abut 60-70%
The top cooling passages weren't hot the bottom was.
I removed the head and cleaned the passages with a screwdriver and ice pick.
After the clean it ran(still runs) great.
Turns out the 40 was on a pontoon that NEVER got flushed after use in salt water

Do like Racerone suggested remove the head and inspect.

Did you check the bypass?