Overheating 454

[Wes Hawkins]

Hi Everyone
Its been awhile since I have been on the forum, I got my boat fixed and up and running. I have however taken on a job for a friend who overheated his inboard 454. There was water in the crankcase, water in all the cylinders. He found that the impeller was shot and replaced it after he had overheated it twice. I figured this would be a cut and dry head gasket or cracked head issue but after pulling the heads and having them pressure tested and magnifluxed and finding no warped head surface or cracks I am stumped. I also could find no cracks in the block. There was a lot of water in this engine more in the cylinders than in the crankcase but what should be obvious isn't.
This is an open cooling system unlike that of a car so how do you go about pressure testing a cooling system of this type?
Help please.
Thanks, Wes.

 

[Tahorover]

Re: Overheating 454

Sounds like you were pumping your cooling system full of exhaust from bad manifolds/risers. Testing method:
http://forums.iboats.com/showthread.php?t=288629

 

[Bondo]

Re: Overheating 454

Sounds like you were pumping your cooling system full of exhaust from bad manifolds/risers. Testing method:
http://forums.iboats.com/showthread.php?t=288629

Ayuh,... I agree,... 1st suspect is the manifold to riser gaskets...
or, cracked manifolds...

 

[Wes Hawkins]

Re: Overheating 454

Thanks guys for tip. I tried this method only using water and saw no leaking anywhere but the acetone makes since. I was going to make set up to pressurize the manifolds but will try this first. The owner now says he not sure how many times he used it after it overheated but now thinks it was a lot more than he originally thought. I did find a suspect spot on the left cylinder head where the gasket looks like it lost its seal. I also found rust staining in the intake manifold in the runners for number 7 and 8 cylinders. It looks like it might well be a blown head gasket and it was pumping water throughout the rest of the engine.
Wes