Life span of thermostats?

I have 92 60HP Johnson. I have done the upgrades to the cooling system and put a new waterpump on last year. I am going through thermostats like crazy. They all fail to where the engine starts running too hot. One even had the plastic housing go to pieces. I seem to get 6 months out of each before the temp gauge starts climbing. Tonight I ran it on the hose and noticed it running 3/4 up on the gauge. Took the thermostat aout and it immediatly went down to C on the gauge. I don't want to run it without a thermostat because it ran real rich while on the hose with no thermostat. I could tell it didn't like it. So what can I do now. I am using the OMC brand thermostats from the dealer. It has an element encased in a black plastic housing.

Re: Life span of thermostats?

When you installed the new waterpump, did you use the new thermostat spring and cover? How many rpms at wide open throttle boat in the water, and moving.

Re: Life span of thermostats?

I used the new cover and the correct spring. I am taching 5800-6000RPM at 35-40MPH as read by GPS speedometer.

Re: Life span of thermostats?

Anything on transom or bottom of boat within 12 inches of motor centerline, that would make bubbles. Motor too high? Reread the instruction that came with the W/P kit, seems to me that there were 3 choices, depending on year of motor. I think that if the thermostat is melting, air is getting in the cooling system.<br />Tattle tale nipple relocated to top of engine?