4.3 Mercruiser overheating

[ibadvanced]

Just bought 1994 boat with a 4.3 mercruiser, 1 st time out it started to overheat at full throttle and also at idle, but at cruising speed 25 mph it was fine. after checking the engine compartment I noticed water dripping from manifolds--both are cracked, but just dripping a little. Ordered new manifolds. Also I checked the impellor and it looks fine. Got good oil pressure and dosn't seem milky. I've only run it for 30 minutes or so. Since manifolds are cracked, guessing it wasn't winterized at one point in it's life, could there be internal engine problems? It dosn't show any external cracking on engine.

 

[bomar76]

Re: 4.3 Mercruiser overheating

4.3's are notorious for freeze cracking in the lifter valley.
You MAY have dodged a huge bullet if it's just the exhaust manifolds and risers that need replaced. It's a miracle you didn't ingest water.
Didn't you sea trial this boat before purchase?
While the drive was split I certainly would have went ahead and replaced the impeller.....what did you use for new gaskets in the pump?

 

[Don S]

Re: 4.3 Mercruiser overheating

If you are replacing the manifolds, replace the elbows also. They may be getting plugged up which could be causing your overheat at high loads.

 

[ibadvanced]

Re: 4.3 Mercruiser overheating

Like a dumby I took the old guys work the boat was fine. The impeller looked new as did the gaskets and no tearing. Not sure if I ran it long enough to ingest water, looks like he just change oil.

 

[Bondo]

Re: 4.3 Mercruiser overheating

Ayuh,... Welcome Aboard,....

It sounds like that motor might have had a 1/2azxed winterization recently.....

It's entirely Possible the they only found the Block drains,+ missed the Manifold drains....

I agree with Don,... Replace the Manifolds,+ Risers as sets.....
I also agree with Bomar that Impellers are Replaced, rather than Inspected....
What did it's housing look like when you had it apart,..??

 

[ibadvanced]

Re: 4.3 Mercruiser overheating

The housing looked fine, no real wear or burn marks. Is that what you meant?