Thread: Water in oil
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Old 02-08-2012, 02:55 AM
Thaiwake Thaiwake is offline
TT Regular
Join Date: Jul 2010
Boat: Mastercraft X Star 2004, Indmar MCX 5.7L
Location: Southeast
Posts: 42
Water in oil


I am having trouble with my 2004 MCX on my X Star. I bought the boat after it had been run in saltwater and have been restoring the engine. I put an orca cooling system in it that runs coolant through the engine block and raw water through the heat exchanger and out the exhaust.

I think it is the exhaust cooling water backing up in the engine. I did a compression test and found no compression on the number 3 cylinder. Took the head off and found an intake valve stuck open.

The other cylinders were fine but I am thinking that because of the lack of pressure from this cylinder the exhaust cooling water has been sucked back into the engine and mixed with the oil. I had new head gaskets and can't see any external cracks or damage to the block, although I can't be sure there isn't anything internal.

Looking back down the cast iron exhausts, which are also new, I can see rusty water droplets both outside the jacket and inside. There shouldn't be water running inside so I can only assume that it is somehow getting there from the outside of the exhaust.

Is it likely that the engine can suck water if there is a lack of compression on only one cylinder?

Does anyone else have any idea on how water can be getting into the oil?

Thanks in advance!
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