1980 nautique running hot

[jforce]

I have a 1980 with a pcm 350 chevy that started running over 180 but less than 200. I have replaced all the water hoses, thermostat, and impeller. The engine seems to run ok but the exhaust mainfolds are getting too hot. Thanks for any help.

[horkn]

Did the impeller shred?

If so, did you look for impeller chunks in the t stat housing? They like to hide there.

Also, have you checked the strainer for weeds and debris?

[rpernell]

just went thru that. I caused the problem myself by using an auto t-stat.
engine stayed at 200 plus. finaly compared t-stat i used to nautique stat
it lets much more water flow out of engine when it opens. I also went to
a colder stat (opens at a lower temp)

[WakeSlayer]

Carbed motor should have a 143* stat. Tighten all your hose clamps frequently.
How is the flow out the back end. Circulating water pumps do fail, too.

Get a laser IR temp gun, they are cheap, and a really good way to pinpoint engine temps everywhere on the block. The only place that should be much above operating temp is right where the exhaust exits the heads into the manifolds.

[jforce]

With this being an 1980 with a chevy engine the thermostat is very specific. I replaced it with a pcm 143 degree thermostat. There is no sea strainer, thinking of putting one on? I have replaced the hose from the hull to the raw water pump. New clamps and all tight. The impeller is fine. No damage,cracks, or missing pieces. It was new at the beginning of the season. I checked the trans cooler to make sure no clogs and it is clean. A few weeks ago I noticed the temp guage started to be higher than normal. I also noticed the exhaust steaming.(learned that for this site). Today I cleaned out the water jackets on the exhaust manifolds. I am thinking the may be clogged but would both sides happen at the same time??? Is there a way to check the volume of flow on the raw water pump? I forgot, also replaced the circulation pump. I know i am rambling, thanks again for any help!

[WakeSlayer]

Where did you get the circ pump?

[thager10]

I used to get an air lock in my Hydrodyne Ford 302 much like you describe. Would solve it by bleeding hose by hose around the engine ensuring water flow at each. Seemed to happen each spring and anytime work was done with cooling system. Cooling system would not clear itself. Also could check for sediment in block using stiff wire in drain holes. Rust flakes can build up there and reduce flow.