Water in crankcase

[Dusty 5]

Recently bought boat, 87 OMC with chev 3.8 ltr. 1 hour on the water, and engine started running rough, shut down and noticed milky oil mixture coming out of vent hose, (water in oil) No water in cylinders, just in crankcase. Took boat home and drained 2.5 gal of fresh h20/oil mix out of oilpan. Any ideas as how it got there.

 

[JustJason]

Re: Water in crankcase

yep.... 90% chance you have a cracked block, in which case the block is junk
10% chance you have a leaking intake manifold gasket. in which case you can pull the manifold and look signes of leakage between the water passages and the heads.

 

[chiefalen]

Re: Water in crankcase

While you got that head off pull off the t-stat housing completely off the head.

See a hole in the water jacket behind the neck of the t-stat,from the water jacket into the push rod hole. Rusted out maybe. Touch it with screwdriver.

 

[Dusty 5]

Re: Water in crankcase

That is kind of what I was thinking, but will check it out further. Worst case , if the block is cracked can an ordinary auto block be used? will the marine stuff bolt up OK, or is there other things to consider. 3.8 engines are not that hard to find. Thanx for the help.

 

[chiefalen]

Re: Water in crankcase

If you replace motor go with a 3.0.

 

[Dusty 5]

Re: Water in crankcase

Everything will bolt right up? Any ideas as to what years blocks would be the same?

 

[chiefalen]

Re: Water in crankcase

Up to 89' will, but if you get a 140 you will get 5-10 more hp.

I just installed a 140, swapped out a 120.

 

[JustJason]

Re: Water in crankcase

Chiefalen..... he's got an OMC 3.8.... not a MERC 2.5/3.0L.....

 

[chiefalen]

Re: Water in crankcase

Maybe i should stop posting i thought it was a 3.0. 3.8 is a v 6.