Any Ideas? OMC 140 Mystery Water in oil

[Neverquit]

Well we survived the winter, most of the cows are calved and out of the corrals now so it is time to start playing with toys again.

Neighbor brought his boat over as he wanted me to re seal his upper gear case and fix a few other small problems.
1985 OMC 140 4 cylinder.

Looking it over without starting it the engine oil was reading very high.

Asked him if it had been winterized, as far as he remembered it had been but it was 3 years ago, boat had been stored inside an unheated building.

I removed a cup shy of a gallon of water out of the oil pan.
I then blocked off the exhaust manifold and pressured the block up to 15 psi for 36 hours, no leaks.

Next I ran it in a tank for 40 minutes, let it sit overnight and checked it again and it did not put any more water into the oil.

My thoughts are if it passed these tests it should be good to go but still no explanation as to where the water in the oil came from.

Any ideas?

 

[Scott Danforth]

could have come from the manifold

 

[Neverquit]

could have come from the manifold

I thought about that, I checked each cylinder with a light and did not find any corrosion.

I do not know what the fluid capacity of the manifold is.

I tried filling the block and head with the exhaust blocked off.
I filled the system using a funnel and the water bottles the owner left in the boat and the quantity to fill the block and head was just under a gallon.

Real close to what I had drained out of the oil pan.

 

[kenny nunez]

If the boat somehow filled with rain water then the small breather hole on the fuel pump could be the culprit. I know you said the boat was stored indoors but maybe the owner forgot about that. Putting air pressure on the block will tell what may have happened. On the GM inline engines there is a very thin area in the block on the starboard side at the bottom of the water jacket, that is where they will rust through.

 

[Scott Danforth]

the 2.5/3.0 has about 1.4 gallons in the water jacket and about 0.7 gallons in the exhaust manifold

you may have sediment in the block (very common on raw water cooled motors)

another thing to look at with your neighbors stringer 400 is the 3-piece vertical drive shaft that goes thru the water pump. where the lower shaft and the mid shaft meet, the splines like to strip.

inspect the splines. if they are involute shaped, thats good, however if they are pointed, then they are worn. also inspect the ball gears

 

[Neverquit]

Update for what it is worth.

After not being able to determine where the water in the oil came from I ended up resealing the upper and replaced the water pump.

Test ran it in the tank for a good hour, everything worked as it should and no more water in the oil pan.

Neighbor took it out fishing this past week and by day 3 on the lake the oil turned into a nasty white milk shake.

In a way not really surprised as the source of the original water in oil was never verified.

Compression test was good and even, no signs of moisture/water in cylinders.

Unless someone has another idea I think it is time to condemn the block, guessing a crack that is opening up once the engine is hot and being worked.

My thinking is the amount of water originally removed from the pan far exceeded what could have come from a cracked head or bad head gasket but did closely match the amount the cooling jacket holds.

He has a spare engine that was developing a bottom end knock so time to tear it down and see if the block can be salvaged.

On a better note I finally dug my boat out of the shed and cleaned it up.

Will test run it today and hopefully get it wet in the next few days.