84 Black Max 150 runs hot at full throttle

[wimico]

Motor has new stats and complete new water pump (both twice) but tends to run hot above 3200 rpm. It has excellent water pressure and pee stream and at 3200 doesn't run over 160 degrees. Above 3500 to around 4000 rpm the temp will immediately go to 240 degrees and start steaming. Throttling down will reduce the temp.
Maybe a bad head gasket?
Your ideas are greatly appreciated.
Thanks to all.

 

[glenn property of pam]

Re: 84 Black Max 150 runs hot at full throttle

what kinda of boat and set up? e.g is the motor high on the transom like on a bassboat

 

[Faztbullet]

Re: 84 Black Max 150 runs hot at full throttle

Could be poppet valve problem....

 

[wimico]

Re: 84 Black Max 150 runs hot at full throttle

what kinda of boat and set up? e.g is the motor high on the transom like on a bassboat

It is on a large pontoon boat.