5.7L MP Thermostat

[wired1236]

Guys

My '06 Marine Power 5.7l seems to run real cold. Never over 130 deg and takes a long time to get warm. I ran it in the driveway at idle for over 5 min and never got much above 100 deg. I took a picture of the thermostat for you guys. I've tried to take it out but am nervous about prying the what others call the plastic retainer. Does the stat look stuck open to you? It seems it is to me. Maybe I just don't understand how it closes off the water flow?

I also noticed one riser got quite a bit warmer than the other. The starboard side seemed to stay real cool and the port hot. Not so hot that you couldn't keep your hand on it for a while and definatly not smoking the hoses but just a big difference from the other side. I took off the hoses going from the stat housing to the riser and it's all clear. I'm probably just concerned about nothing. I didn't really rev the motor since it was on the flush kit.

[chpthril]

That whole thing is the thermostat. Scrap the gasket away and you will see the seam where the thermo is set into the housing. Just work a small flat tool under it and it should pop out.

[dom w. forte]

You have to pry out the white plastic outter insert that holds the stat to the housing, and they do get weak with age and can either run to hot or to cold , running to cold is just as bad as running to hot , so if you dont know how old it is I would change it.

[duffymahoney]

Whats the proper temp thermostat? My lake is pretty cold.

[dom w. forte]

It varys per engine and manufacturer, but normally 140 to 160, most injected engines run 160, with heat exchanger about 170.
Computor strategies are based on temperture for proper timing and fuel mapping.
With a injected motor, a stuck open stat is like a carburator with the choke on, running richer then it should.

[wired1236]

I did get it out w/o breaking the plastic keeper. I put the stat in hot water with a temp gauge. Opens right up around 140-150 deg. It is a 140 deg stat as it's stamped right on it. It also seems to hold water when closed. My guess is the temp guage is a little off and everything is really OK at this point. Napa even had a new gasket in stock! Go figure! It's a carbed engine and it's just a little cold blooded for 3-4 min. It usually takes 2-3 starts. This will be my last carbed engine, of course I said that with my last boat too. It just didn't work out this time.

I've also done some reasearch on the uneven riser temp. I've been told this is pretty normal at idle speeds. The flow of the water isn't even, especially at low idle.