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1989 43 Cobra Temp

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pat_the_pom

Contributing Member
When running the engine on the

When running the engine on the muffs my temp guage goes up to 160 and stays there as long as I like. However when the boat is running in the water the guage only goes up to 120 at any speed.
Is this a problem? I fitted new external and internal water pumps at the start of the season.
 
The 120 in the water sounds to

The 120 in the water sounds to me like the T-Stat is stuck open although I'm not sure why it's going up to 160 on the muffs unless it just runs hotter on them. How high are the RPM's when running on the muffs?
 
Which once again proves that r

Which once again proves that running on muffs is no way of testing an engine and the systems!
Relay on the 'in water' readings. Your water supply is probably insufficient when running on muffs.
 
That depends if You are runnin

That depends if You are running a raw water cooled or fresh water cooled engine. Technically both are correct.
Raw water cooled (salt water running) use the 140.
In lakes/fresh-water/fresh water cooled You may use the higher one.
 
Thanks Morten. Can you tell me

Thanks Morten. Can you tell me how does the T stat come out? When I had the housing off before I noticed that the stat is actually up in side the housing and I couldnt see a way to get it out.My system is raw water cooled. Why the difference if I only run in fresh water?
 
It's held in with a rubber

It's held in with a rubber o-ring. Just reach in with a pair of pliers and pull it out. The new t-stat comes with a new o-ring and gasket.
 
"In a salt water run engine it

"In a salt water run engine it is important to keep the temp below when the salt starts to get into crystals. However that is not too ideal when it comes to combustion. That might be 'corrected' when running in fresh water, lake or internally. Just watch the car temp and see what that one is on."
 
"This is a common problem on r

"This is a common problem on raw water cooled IOs used in salt water, I find I have to replace the thermostat each season or it gets sticky and the engine runs too cool unless it's on plane and then it runs at its usual 160. When they get sticky (does not close all the way) the engine will not warm up when idling and may only reach 120 degrees at low rpm running. I have tested them in a pot of boiling water and what I found is that the used ones vs the new ones don't close all the way and respond to water temp changes more slowly. So just change it!"
 
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