1993 fast strike 150 overheat only at WOT???

[pappyjo]

Hello everyone, I have a 1993 cajun 19' bass boat with a 93 johnson 150, the motor runs well besides a small miss (I havent had it long and will be doing a tune up soon).

I am getting an overheat alarm only when I am cruising at anything over 3/4 throttle. I have been on the water several times over the past month and no matter what the conditions I can make the engine sound the overheat alarm as soon as I hear the alarm I imediately go to idle and wait about 20 seconds for the alarm to stop then shut the engine off, I will then wait 15 seconds and restart after which all is fine until I go to wot again. At anything below 3/4 throttle the engine will go all day without sounding the alarm but it only takes about 1-2 minutes at 3/4 throttle or more to make the sound. According to my water pressure gauge I am seeing about 25 psi at max throttle and I have watched the stream coming out of the back of the motor and its shoots out about a foot at idle and steadily increases as I up the throttle.

I am very unfamiliar with these motors but I have a factory service manual and have started reading, I just thought I would post this up so I could get some actual knowledge to point me in the right direction.

Anyone have any ideas?

Thanks

[ChampioNman]

Don't believe that is a overtemp alarm more like the starvation alarm if the motor doesn't go into SLOW mode at those RPM's.

[pappyjo]

The motor does go into half power mode once the alarm sounds, I have to wait for the alarm to go off then shut the key off and restart the motor to get it back to full power.

[ChampioNman]

Water pressure? Head Temps?