Overheating Problem

[fishfun83]

I am continuing to have overheating problems with my 1997 Yamaha 80 hp 2 cycle motor. I have checked the impeller and it looks excellent. Replaced it last year. Checked the thermo switch and thermostat and they all checked out good. Cleaned the cylinder heads, which were pretty caked with corrosion and at that point thought I had the problem resolved but it again sent the buzzer going after about 1 hr 15 minutes of operation, mostly at slow idle speed. Today I decided to clean the cylinder heads of corrosion. While cleaning, I noticed a fairly uniform slot at the bottom of the cylinder head in the water path. My concern, even though it looks uniform in size and not jagged like you would expect, if it were there by corrosion, is that it is not suppose to be there and I am losing my cooling flow, and therefore, over heating. Can anyone offer any help? See pictures (2) below.


http://s1192.photobucket.com/albums/aa334/fishfun83/

[jayay222]

PRV Pressure Relief Valve / Poppit Valve

Hi,

Not sure about the photos, but does your motor have a PRV (pressure relief valve AKA poppit valve)? If its stuck open or not fully closing you may overheat at low speeds because your not getting enough water pressure to get through the cylinder head. I just replaced mine, complete with pressure relief valve, spring, cover & gasket. I was overheating at higher RPM's because mine was stuck closed.

Also, if you took your heads off, make sure you replace the gaskets. I made that mistake last week by reusing the old ones & had leaks.

Jason