mercruiser 3,0 when ran 10 minutes starts running very bad

[norcal racer]

This motor overheated got pretty hot it melted all cooling parts in drive exhaust boots ect. I repaired all and engine runs perfect and smooth. Afetr 10-15 minutes Im guessing when engine is good and hot it starts running like crap. Pops through carb and sounds like a leaking exhaust gasket by the popping sound the more i ran it the worse it got. Go back the next day same thing runs perfect until it gets good and warm, temp gauge is not showing its hot. Also i did a compression test when i did the work and it was fine, no water in oil.

 

[alldodge]

This motor overheated got pretty hot it melted all cooling parts in drive exhaust boots ect. I repaired all and engine runs perfect and smooth. Afetr 10-15 minutes Im guessing when engine is good and hot it starts running like crap. Pops through carb and sounds like a leaking exhaust gasket by the popping sound the more i ran it the worse it got. Go back the next day same thing runs perfect until it gets good and warm, temp gauge is not showing its hot. Also i did a compression test when i did the work and it was fine, no water in oil.

I'm thinking your head is warped. Get the engine running long enough for it to start messing up, then do a compression test

 

[fishrdan]

I repaired all

Specifically, what did you repair/replace? What condition was the old impeller in and was it missing and vanes, and if it was missing vanes, did you track them down and remove them?