'76 75HP 'Rude runs too cold

[jerrypark1]

Model#75643D. I can never seem to warm this engine up. Even after a WOT run across the lake, or even idling through no-wake zones, it never seems to get hot. I can consistently keep my hand on the head indefinately in all circumstances (which is probably causing my excessive smoke problem as well). I've tried new thermostats, and replaced the impeller (PM) but nothing has changed....cold and smokey. Obviously, the thermostat isn't functioning properly (even though I've tried 2, and boiled them to make sure they open and close properly) or possibly the water is finding an alternate path by the thermostat that I can't see. Any ideas out there?

 

[OBJ]

Re: '76 75HP 'Rude runs too cold

Take another look at the relief valve, spring and seat. The valve should not be deformed and the seat good. The spring may have lost some of it's tension over the years. This could let the releif valve come open farther than is normal. Is the t-stat OEM or generic part like Sierra?

 

[jerrypark1]

Re: '76 75HP 'Rude runs too cold

The replacement thermostat is generic....sierra I think. It's the only one I could find. I'm pulling it apart tomorrow (gotta find another exhaust leak too) and will take your advice and check the relief. Springs are both pretty strong still though. Any ideas where I can find OEM parts? I wish iBoats carried a bit more of the original stuff. And thanks for the help.

 

[jerrypark1]

Re: '76 75HP 'Rude runs too cold

Well, I replaced the springs, seats and valves. New gasket for thermostat, and for housing as well. No change, the motor still runs too cold. I can run WOT across lake, or idle through no wake zones all day without ever warming up the engine. I would say it's in the 80-90 degree mark (65 degree water, on a 75 degree day). Any ideas of where to look next would be greatly appreciated....