1986 3.0 OMC Water In Oil After 6th Trip

[Renken1]

Hello everyone. I have an '86 Renken Bowrider with the 3.0 OMC / Sterndrive. At the beginning of the season I changed all the fluids including the engine oil. I have had it out 5 trips this season without any issue ( I check the oil level before and after each trip ). Just for history / usage purpose I normally cruise around with my wife at aproximatly 15-1800rpm, and it has never seen over 3200rpm since I've owned her.

Yesterday I took her out, eased around the lake at 1800rpm for about 15 minutes, then planed her out at 2900rpm for about 3-4min, and back down to 1800rpm without any issues. About 10min after bringing it back down I began to notice a slight intermittant miss. I had the wife drive while I went and checked the engine. When I opened the door there was white oil mixed water along the right side of the head where the exhaust bolts up and it was bubbling at the gasket. Under the engine there was a gallon or more of white oil/water mix, pulled the dipstick and it was nearly to the top with the same white mix. With the engine still at 1800 i decided to head for the dock which was about 10min away. Once there I left it idling, put trailor in the water, and attempted to load it but it bogged everytime i would idle up and it finally quit. Once on level ground I checked the oil and it was over 1/2 way up the stick. I estimate it took in at least 2 gallons of water.


My question is are there any gaskets that could have failed that would let water enter the block? It just seems odd that I've had it out so many times this season without issue. Anyone have any ideas on what could have went wrong?

 

[jerryjerry05]

Could be: the manifold/ riser is leaking water back through the valves?
Pull the plugs and see if there is rust/ water/ oil?
Pull the manifold and check the intake passages.
Do a compression test.

 

[Renken1]

Thank you for the suggestions Jerry. While I am an experienced mechanic, I have never dealt with any sort of inboard boat engines. I have no idea how the exhaust / water is kept seperate. I will start disassembling it in a few minutes to see if I can spot anywhere it can be coming in from.

 

[Maclin]

With that much water getting into the crankcase I do not think it could be getting there from the "top" of the cylinder thru the rings, pretty sure the engine would hydrolock first (or bend a rod). A pressure check of the engine block cooling passages would tell if there is a crack somewhere, that would be the most likely scenario to get that much water that quickly into the crankcase.

 

[Bulbash]

Probably it is a cracked manifold or riser. Pull it off and see if the passages are black. If manifold cracks and lets water through it would steam clean the exhaust part of the manifold...

 

[bruceb58]

Your block is cracked. You can't get 2 gallons of water in your oil from bad manifolds.

 

[vinnie1234]

I agree with Bruce. That much water in the manifold would cause your engine to stall. It would be like pouring a bucket of water in the carb. If it didn't stall from lack of burn, the engine would suck it in over the next intake stroke and hydrolock instantly. You would notice that. If I were you, I wouldn't want it to be a cracked block, but what other mechanism would allow that to happen? I would start looking for a used motor or basket case boat to scavenge some parts. (bummer)

 

[Renken1]

Ok guys, I had a chance to work on it. I pulled the manifold off and it had water inside the exhaust passage. #2 and #3 exhaust ports in the head appeared to have moisture in them, while 1 & 4 were dry and chalky looking. Using a tape measure I gauged the extra amount of water in the oil 1st by measuring the distance from " add 1 quart " to the " full " mark on the dipstick and it appears that it has right at 2 quarts of water in it. I know I originally stated 2 gallons, but I was obviously still in shock and talking out of my backside, sorry about that. Since the total runtime on that trip was about an hour, is it possible that it had a gasket failure? The front piece and the rear elbo was both sealed with RTV, so I couldn't really see an obvious spot on them. The bolts for the manifold itself wasn't very tight at all, took VERY little effort to loosen them up, and the gasket wasn't in that good of shape either.

Thanks to everyone who took the time to reply, and any further input will be greatly appreciated!

 

[Howard Sterndrive]

I would do an easy test to eliminate the block. Pressure test the cooling system.

 

[Renken1]

thank you Mr. Howard! I will see if I can round up enough stuff to do that this morning. BTW, is that the factory OMC engine color? Someone painted mine all black, and I always wondered what the factory color would have been.