Problem with mercruiser 5.7L (2005) - water in oil

Hello,
I have a Mercruiser 5.7L engine (8 cylinders) 2005, that overheated during activity, probably because the water holes were blocked (due to plants that grew up in the warm marine water).
The marine mechanic checked the compression in the cylinders, and saw that on one side (4 cylinders) there is water and on the other side there is low pressure (in one of them there was no pressure at all(
The mechanic said that it is probably cracked block, and the engine need to be taken out and examined.
Do you have any idea for something else I should check before replacing half of the engine?

Thanks in advance,
Ilia

I would replace the whole engine. Cheaper in the long run and you will get a warranty. Foolish to do anything else.

Sometimes the head gasket goes in a overheat condition.

In such case it should only be replaced? if it actually has a problem it should be seen clearly?

Does the fact that there is problem on both sides of the engine (both cylinder groups) have a meaning? If it is the block, it means that there are two cracks in it?

Thank you for the answers,
Ilia

Docksidemarineservices said:

I would replace the whole engine. Cheaper in the long run and you will get a warranty. Foolish to do anything else.

Click to expand...

Ayuh,.... It means ya oughta listen to DCMS, 'n replace the complete Long Block motor,...
Just reuse the accessories off the motor ya Cooked....
(I'd look over the manifolds real closely, 'n replace 'em if there's Any doubt to their integrity,...)

Rebuilt, yer lookin' at $1,500., 'n Up, plus Labor....

If you do pull this engine apart you will find cracks in both heads. This is a common result during an over heat. Very rarely does a raw water cooled marine engine experience head gasket failure due to no pressure in the cooling system.

If the heads are bad, it will be cheaper in the long run to get a rebuilt long block. Stay away from the rebuilder in South Florida.