mercruiser 120 hp - 1988 - water in oil

[shraigeed]

Quick question regarding water in the oil. I have a 1988 Mercruiser 120 hp I/O. Last year I forgot to take the plug out and the boat got quite a bit of water in it. Because I only had it out 3 times I didn't change the oil but I did winterize the rest of the boat. Now this year there seems to be water in the oil. I changed it a couple of times and put some seafoam in it. When I put the muffs on it it seemed fine but I took it out for the first time yesterday and when I checked the oil it was milky. I have heard various opinions as to what it could be. From a cracked block (that seems unlikely since I did put antifreeze in it last fall), a head gasket, or the latest one I heard was that it could be water in the exhaust port. Is there anyway to test any of these? And also, I had it out for a couple of hours yesterday and it ran fine. Could I have done more damage to it by running it like that? What's my next best course of action?

 

[Uraijit]

Re: mercruiser 120 hp - 1988 - water in oil

Simply "putting anti-freeze in it" isn't winterizing. Cracking a block this way is more likely than you think. You've gotta drain all the water OUT, and then you can pour a little anti-freeze in there, as extra insurance...

Start with a compression test, and inspection of your exhaust risers.

 

[shraigeed]

Re: mercruiser 120 hp - 1988 - water in oil

Simply "putting anti-freeze in it" isn't winterizing. Cracking a block this way is more likely than you think. You've gotta drain all the water OUT, and then you can pour a little anti-freeze in there, as extra insurance...

Start with a compression test, and inspection of your exhaust risers.

Sorry, I should have clarified. I drained the block, blew out hoses, etc, added the antifreeze and blew the hoses until I saw the anti freeze coming out. For some reason (I guess because it was my uncles boat before he died and he always did it) I change the points, condenser, plugs, fuel filter, etc every year. Naturally I also did the lower unit. The only thing I didn't do was change the oil since I had it in the water only three times. What's better news... water in the exhaust risers or what? Is that a real major repair if there is water in the exhaust or something I can do myself?

 

[shabazz18]

Re: mercruiser 120 hp - 1988 - water in oil

Do a compression test. That will eliminate the block. Then a leakdown to check valves. If you have a bad exhaust valve, water can come up the exhaust and leak in through there.

I had a cracked head causing my chocolate milk problem.

 

[Maclin]

Re: mercruiser 120 hp - 1988 - water in oil

A compression test will not expose a cracked internal water passage in the engine block. A pressure test of the cooling system will.

A compression test will show the general health of an engine regarding cylinder sealing by showing compression pressure/psi, a leak down test can help determine where the leaks are (valves, head gasket, pistons/rings).

 

[Maclin]

Re: mercruiser 120 hp - 1988 - water in oil

Shraigeed,

Of the two scenarios 1.)Cracked internal cooling passage in the engine block or 2.)Corroded risers or bad riser joint gasketing leaking water into open exhaust valves I choose #2 as it can be cheaper to fix.

BUT you have to catch it early and get the water out of the cylinders before it sits. Also if it hydrolocks out on the water you must recognize why the engine does not want to turn over and not keep trying to start it and bend rods or worse. If it does catch and has enough water in a cylinder it can cause major internal damage.

Usually bad risers/manifolds/gaskets will not allow a bunch of water to get into the block as it has to enter a cylinder first then go past the rings. A significant amount of water in the block is usually the sign of the end of life for that engine block.

 

[shraigeed]

Re: mercruiser 120 hp - 1988 - water in oil

Thanks for the advice. I really appreciate it! I am surrendring though. I'm taking it into the shop next Tuesday. Whatever it is it sounds like it's over my head. The only thing the guy at the shop said to do before bringing it in is to take the plugs out one at a time, run it, hold my finger over it and see if I have water coming out. He said that it would tell me if it was the head gasket. I'll do that but I'm afraid to do anything more. I don't want to make matters worse. It already sounds like it could end up being expensive. I suppose I could donate it to a technical college or something for a tax write off! My uncle has got to be rolling over in his grave!