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Old 02-08-2012, 02:55 AM
Thaiwake Thaiwake is offline
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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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Old 02-15-2012, 11:49 PM
Thaiwake Thaiwake is offline
TT Regular
Join Date: Jul 2010
Boat: Mastercraft X Star 2004, Indmar MCX 5.7L
Location: Southeast
Posts: 42
Released the stuck Intake valve and the engine is running great again. I was suprised that a stuck valve would cause so much water to be sucked into the engine. Incase anyone has any problems with water in the oil and it isn't because of the head gasket or block, then do a compression check and make sure there is full compression on all cylinders, a loss of compression will cause the exhuast water to back up into the engine.
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Old 02-16-2012, 08:21 AM
NatesGr8 NatesGr8 is offline
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Join Date: Jul 2004
Boat: 05 X-45
Location: CT
Posts: 507
Thanks for the follow up. How do you like your closed cooling system?
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Old 02-16-2012, 08:42 AM
thatsmrmastercraft's Avatar
thatsmrmastercraft thatsmrmastercraft is offline
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Join Date: Sep 2008
Boat: 1977 Stars & Stripes
Location: St. Paul, MN
Posts: 18,574
Did you determine the cause of the valve to become stuck? Bent valve?

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compression, mcx, oil, valve, water

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