1991 5.7 mercruiser overheating

[akamoonman]

I Hope someone can help me because im at my witts end

My 5.7 1991 mercruiser is overheating and i don't know where to go from here

1. changed impeller
2. removed thermostat (housing is somewhat worn)
3. Repaced water circulating pump
4. removed risers and manifolds and cleaned the out
5. There is waterflow ging through the engine.

Any advise would be appreciated

 

[Bt Doctur]

Alpha 1 or Alpha GEN II

 

[akamoonman]

Gen 2

 

[Bt Doctur]

If this is a high speed overheat, drain and drop the lower unit, place muffs on lower unit and turn water on full.
You should find water leaking from under the water pump cover.This is allowing the pump to suck in hot exaust gas and cause the overheat.
The cure is to use a GOOD ,FINE cut flat file and level the surface untill the SS plate sits perfectly flat, with no wobble and you can`t pull a sheet of paper from under it.
Now install the gaskets , and retest with the muffs. Should find no leaks from under the pump assembly

 

[sandkicker]

....and replace the t'stat... and housing if wear impacts t'stat seating or gaskets surfaces.

 

[akamoonman]

DR.. guess im removing the lower unit and trying the rabbit ear thing.. I did the impeller once before and had no issue.. this time when I did it I actually used all new pieces. that may have been my problem..