2009 4.3 mpi running hot

[Alkibar]

Changed impeller and the stat water comes out of both sides of transom equal
Without thermostat runs all day cold with 160f tstat runs at 195 to 200f risers are cool manifolds are hot to touch and thermostat housing can hold hand for 4 seconds
Pulled belt off water circulation pump and no friction or loose or noise
I'm stumped please let me know if any thoughts

 

[Alkibar]

Raw water cooled removed from ocean daily

 

[Scott06]

Have your manifolds and elbows been inspected or replaced? If you are in salt and havent replaced your manifolds pop the elbows off and look in cooling passages

 

[QBhoy]

Has this overheated previously and the reason you changed the impeller ? If it has, you may have melted and dislodged your flappers and have them stuck down the exhaust somewhere. Causing a restriction in water flow.

 

[alldodge]

Being raw water cooled the motor should have 140* thermostat. The 160* can cause the salt to deposit inside the motor. Can also have Bravoits issue.

Put a piece of clear hose at the thermostat housing hose which comes from the raw water pump, to check for air bubbles

 

[Lou C]

I would
Definitely check the manifolds and elbows if never done and you are in salt water
Also test the stat in a pot of hot water with a metal thermometer and see what temp it starts to open at. And yes a 140 will be better for salt
If your last impeller came apart you will need to find the pieces. If an Alpha drive could be in the PS or fuel cooler if a Bravo could be in the stat housing.

 

[Scott Danforth]

EFI and raw water cooled is 160. Salt water is better with 140f T-stat, however engine needs 160

Did you verify the temp with an IR temp gun?

Moat likely your manifolds are plugged. In salt water, you should have changed them at least once in 13 years, if not twice

 

[Lou C]

Here in salt I’ve done mine every 7 years at least and I have not had an overheat due to the inevitable corrosion or water leaking back into the engine. Even with the old Batwings that had restrictive cooling passages and clogged pretty easily.
Look at how much larger the passages are on the 2 piece system that I replaced it with

 

[poconojoe]

A little confusing...
I'm, by far, not an Eglish major...
The use of periods and commas would help clarify what you are trying to convey.
If English is not your primary language, I sincerely apologize.