water in oil

steve 379 · Sep 24, 2011

hello got water in oil so we took this motor stripped it down in replaced all the gaskets in the motor did not find any cracks had the heads rebuilt manifolds checked put it all back together ran good for two weeks no water in oil then we changed impeller/water pump then we got water back in the oil again is there anything that we are missing thanks

Don S · Sep 24, 2011

Re: water in oil

is there anything that we are missing

Just a couple of minor items, like what kind of engine, and how much water? Thimble full, quart, gallon ??????

steve 379 · Sep 25, 2011

Re: water in oil

it is a 1975 351w mercruiser 233 when we started it up after we replaced the impellar the oil pan filled up fast turn to milkshake in no time minutes lots of water. thanks

Bondo · Sep 25, 2011

Re: water in oil

steve 379 said:
it is a 1975 351w mercruiser 233 when we started it up after we replaced the impellar the oil pan filled up fast turn to milkshake in no time minutes lots of water. thanks

Ayuh,... Cracked block, or cracked intake manifold...

steve 379 · Sep 25, 2011

Re: water in oil

well cant do nothing about a cracked block but i will take the intake off and send it to a machine shop maybe will get lucky thanks for the advice.

mercfixer · Sep 27, 2011

Re: water in oil

In thirty odd years of service, I have yet to see oil contamination that was not easily diagnosed. Start with the most common cause. The exaust is the first thing I would inspect, seven years seems to be the magic number in salt water for riser and manifold life. The next test I would go to is compression testing of the cylinders. If that shows no conclusive results, cylinder leakdown testing would be my next move. Freshwater cooled systems are the easiest to eliminate by simply pressurising the heat exchanger with an automotive radiator pressure testing tool. Diagnosis is what it's all about. I have encountered alot of parts changers over the years, and they don't have alot of loyal customers.
Hope this helps

steve 379 · Nov 14, 2011

Re: water in oil

well new question the motor in this boat now is a mercruiser 233/351w it is bad so got a mercruiser 225/302 they are both small blocks can i used the 225/302 as a replacement the trans is not the same would need to change the trans from the 351w to the 302 will this work.
thanks

Bondo · Nov 14, 2011

Re: water in oil

steve 379 said:
well new question the motor in this boat now is a mercruiser 233/351w it is bad so got a mercruiser 225/302 they are both small blocks can i used the 225/302 as a replacement the trans is not the same would need to change the trans from the 351w to the 302 will this work.
thanks

Ayuh,... Their both SBFords, it should work Ok...

steve 379 · Nov 14, 2011

Re: water in oil

well i thank you for the reply bond-o will take it too my friends shop in start on it this weekend.
thanks

gunsup007 · Nov 14, 2011

Re: water in oil

Steve please let us know what you find out because I am about to pull my motor apart too, due to water in my oil. Good luck man.

alexr254 · Nov 17, 2011

Re: water in oil

I too have water in oil. But mine came directly after i did an entire rebuild of 2 engines. One with no issues, one with water in oil.

My engines are a bit different then yours being Merc 470's, but same concept.

What it came down to with me is a bad block, looked kind of like the steel cyliners for pistons eroded at the bottom and water must have gotten in. Probably at some point in the engines life, it was either overheated really badly or froze in the winter, since the steel cylinder walls did not look completely flush onto the aluminum block.
All the manifolds seemed ok, and i pressure tested the head... So eventually came to the conclusion its the block.

Please let us know how it worked out for you, hope its not that bad!!

water in oil

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