Getting high temp alarm at 4800 rpm and above

[chasia]

I have 1989 60 HP Merc (OB227117)3 cyl. It will run all day at 4600rpm. Installed new impeller last year. I checked it today and it looks fine. Running wot get alarm, drop rpms back to 4600 or below goes off. Good taletail. After getting alarm and making it back to motor, water is hot but immediately goes to warm. Acts like thermostat but not sure it has one. I'm going to try new impeller. Any suggestions? Thanks!

 

[imported_scott_m]

Re: Getting high temp alarm at 4800 rpm and above

Thermostat or poppet valve? I just changed the poppet on mine...would run hot for anything over 2000 rpms.

 

[chasia]

Re: Getting high temp alarm at 4800 rpm and above

Thanks for info Scott. My problem is that I can't find any external access that would get me to the poppets or thermostat

 

[imported_scott_m]

Re: Getting high temp alarm at 4800 rpm and above

Disclaimer..not knowing your engine...however, follow the water lines and you'll find the thermostat housings. The poppet valve is on the lower starboard side of the block on my v-6.