Oil in Water but no Water in Oil

[3rdDonzi]

Last November I posted about a suprise I found while winterizing. I had some oil in my drained water but no water in my oil. Oil was very clean, even checked with a lighter to the dipstic to see if any oil invisible to the eye would boil, no water.
Have since de winterized and run the boat hard, re checked and changed the oil still no water.
The boat runs great and seems to be well tuned however there has always been an abnormal amount of soot on the transom after a run.
Ran this by my neighbor who restores antique wooden boats and is an active home garage mechanic. He seems to think that there is a leak in the oil cooler letting a small amount of oil into the water but due to different pressures no water enters the oil, hence the oil tat runs through the pipes becomes soot on the transom. I'm not talking about a lot, not enough to affect quantity between oil changes.
Any thoughts would be appreciated.
My boat is a '95 Classic, 350 Mag, Alpha, stock.
Thanks to all,
Corky

[mjw930]

Oil in the water will never reach the temperature required to flash off and cause soot.

Soot on the transom is due to a rich fuel mixture. You state that the motor is stock yet you comment on it being "tuned". By tuned do you mean timing set, filters and plugs changed or are you referring to someone adjusting the carb jets?

In a "stock" configuration most Mercruisers run rich. Unless you are willing to play with the carburation there's not much you can do about that. You should see the transom on a twin engine boat with stock HP500's (carb version) after a hard run!

The oily residue in your water could come from a lot of places but the oil cooler is a likely culprit. However, when they leak they typically let water pass in both directions. Taking a lighter to your dipstick will only identify emulsified water. You could have water in the oil and not notice it until you pull the valve covers or intake manifold. You could also get an oil test done to determine the exact amount of water in the oil.

One other place to look would be the manifolds and risers. "oily" water coming out of the manifolds could actually be byproducts of combustion mixing with the water in the manifolds.

[3rdDonzi]

Thanks for the detailed reply.
You asked: "By tuned do you mean timing set, filters and plugs changed or are you referring to someone adjusting the carb jets?" I meant timing set, filters and plugs changed. Not being a mechanic I may have used the wrong term.
Years ago I had oil that looked like a chocolate shake in an x-18 due to a blown head gasket.
If pulling the valve covers could be revealing wouldn't the underside of the oil filler cap be an indicator? I guess a new oil cooler would be a relatively inexpensive place to start.
One other thing, when I winterized, the boat had not been run in about 8 weeks. The day after a hard run last week I sampled water from the block and manifold ans saw no oil at all.
Thanks Again,
Corky

[MOP]

I think you are chasing your tail! If you had water in the oil it would have colored the oil to some degree, no way would it be as clean as you say, I would put my $$$ on some that was dribbled into the bilge along the way. The soot issue is an over fuel problem caused by any number of reasons.

Phil

[DonziJon]

SOOT: Most of us have been around for awhile, using knowledge we have acumulated over many years.....based on Leaded Gasoline, then Low lead, then No lead, then Ethonal.
I think the Ethonal thing is a BIG change.

I have a low mileage (30,000) 1990 Yamaha Venture (Carburated) touring bike that wasn't used in 2006. In '07 it would only run at OVER 2,400RPM. At highway speeds it ran fine, and had all the power it ever had. BUT: It would NOT IDLE.... Low speed jets clogged?? Ethonal??. Antique Car collectors are having the same problems with cars that don't run very often. The solution seems to be.....you need to RUN the car.

I put 18 hours on my Minx last year...The last tank I ran through the boat came from Lake Winni, NH.... where ..at the time, (Sept '07) you could get NO Ethonal at the gas dock.

[justleft]

I agree with MOP.... Monitor the situation.

[3rdDonzi]

Thanks for the replies. I too am very confidant that there is zero water in the oil but what is puzzling is that before I drained the engine you could have eaten off of the bilge. The oil definately came from the drain plugs. From airplane cowlings I know that a shot glass of oil can look like a gallon. It probably isn't a lot.

[harbormaster]

Personally, I'd live with the soot amd leep the transom waxed. At least You wont have to worry about a lean condition frying a piston...

[CHACHI]

If you think that you may have water in the oil, get a oil analysis done, but a quick test is to drop a half an ounce or so, (be careful and stand back) into a hot frying pan. Hot enough so that when you sprinkle plain water on it the water "dances" in the pan. Wait for the water to evaporate, then drop your engine oil in the pan. If it pops, that is the water evaporating out, if the oil just thins quickly, no water.
Ken