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MerCruiser 3.0 MPI ECT Water in Oil

JohnnyHooligan

New member
Ladies and gentlemen. I have a 2014 Stingray boat my wife bought new for me. It only has 33 hours on it now. I go to a local lake about 2-3 times a year Due to a personal issue I forgot to winterize /drain the water last this past winter. I remembered after our first freeze. I placed boat in heated garage, found the thermostat gasket had pushed out. I replaced the gasket, oil and filter, boat started right up and seemed to run fine. Went to lake to discover it didn't accelerate as quickly. I returned home to find milky oil on dipstick. Drained oil and there is definitely water getting into the engine. I'm an old farm boy who have fixed all my equipment, tractors, for over 50 years. Before I pull the heads any advice is greatly appreciated!(Other than reminding me to winterize! My wife has taken care of that!) Thank you.
 
Ayuh,...... Drain the block, isolate the block from the exhaust manifold, 'n in-comin' water line, then pressurize the blocks coolin' passages with 'bout 15 psi of air,....

Then Listen,....... You'll hear the excapin' air, follow the sound though any openin's,....

If you hear the hissin' through the oil fill cap, the block is busted, probably in the oil cavity, opposite the block's drain plug, on the inside,....

Unfortunately, odds are, yer gonna need a new long block motor,......
 
Ayuh,...... Drain the block, isolate the block from the exhaust manifold, 'n in-comin' water line, then pressurize the blocks coolin' passages with 'bout 15 psi of air,....

Then Listen,....... You'll hear the excapin' air, follow the sound though any openin's,....

If you hear the hissin' through the oil fill cap, the block is busted, probably in the oil cavity, opposite the block's drain plug, on the inside,....

Unfortunately, odds are, yer gonna need a new long block motor,......

Thanks for your advice! I'll need to look for the incoming water line to clarify isolating procedure! I was going to check compression as well.
 
Incoming water line will come from outdrive up the intake and land in the thermostat housing.

The compression test won't tell you anything as you can have great compression ... with a crack into the oil side of the block. Likely given the age of the boat your compression is near perfect.

Worst case a brand new longblock Aka base engine is $3200, reman is about 800 less. If you are handy like you say it's easy to pull the engine , swap all the components over (may need a new manifold if it's cracked) and be back up and running
 
Thanks for your advice, I'll do the air check next. Will it hurt to run it until I can replace long block if needed. Average person probably wouldn't even notice unless oil was checked? Thank again!
 
Well it will blow up eventually from poor lubrication and people who dont check their oil everytime before use deserve whatever happens
 
when water mixes with engine oil :
blown head gasket from an overheat condition
cracked block or manifold from a incorrect winerization
on a V type motor , intake manifold corroded hole under the thermostat
 
If the oil is very milky you have a Cracked block. Since you did not winterize.......

A cracked manifold will only let water into the cylinders when the engine is sitting/off. Less than a pint.
 
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