1990 yamaha 200 hp overheats at high rpm

[RJF]

My 200 yamaha overheats at over 4200 rpms I have changed thermostats prv valve which did help water pressure and water pump.When I changed the t stats and prv valve looking into the motor I did not see much build up of corrosion but i'm not counting out aproblem with the water jackets yet but what i could see looked pretty good.Now my question is it possible with the e10 gas I did have problems with my fuel filter water seperator clogging used 8 filters this year could the jets in the carbs be clogged causing alean condition makeing the motor overheat? when I do get a alarm iback off to idle and the motor cools alarm stops in less than 1 min then i can run at 4000 rpm all day long no problems.Any help or suggestions would be appreciated. Thanks Ron

[boats.net]

Removing heads is the next step to clean water passages. A lean condition can cause detonation, if it has the piston and cylinder may be scored, look at them when you get head off.

[RJF]

Thank you for the the reply I am going to pull the heads this week to see how they look and clean them up. Thanks again boats.net