Water in oil but pressure test ok; suggestions?

[StevNimrod]

Working on a Merc 5.7 stroked to a 383 (Gen + base) with thru-hull exhaust and a mild performance cam.

Got boat out of storage a few weeks ago and did a tune up and fixed a few things on my to-do list. Fired it up in the driveway for about 20 minutes to check timing and set idle on carb. Started fine and ran fine, pulled a steady 17 mmHg at idle. Shut it down and buttoned it up. Checked the oil and it seemed high, but it was clear so I figured it hadn't drained down yet.

Getting ready to put it in the water a few days ago and was hydrolocked. I forgot to run it at 1300 rpm for 45 seconds to clear the pipes after the idle in the driveway. No big deal, pulled plugs and cranked a few times and all was well.

Went for another shot at launch yesterday and noticed oil was still high. Have a remote drain line so I hooked my pump up and pulled 1-2 quarts of water out before hitting oil. Also noticed that my pump stopped pumping but the dipstick still read between "add" and "full". Not good.

Pull drive and spark plugs, block off water inlet, hook up my pressure test fixtures and pump it up to 15 psi. Held for 45 minutes. This setup includes the block, intake, heads, and manifolds. The risers are good too, and were tested during the wait.

I have the Merc Service Bulletin entitled "Gasoline Engines and Water Intrusion" and it appears this one gets written off as "water got in my an unknown way". I'd think a pressure test would show any leak path between the water passages and oil.

Any suggestions on where to look next? Or just flush a few times, fill, run hard, and keep fingers crossed?

 

[dubs283]

Re: Water in oil but pressure test ok; suggestions?

did you pressure test the block when it was warm??

 

[solar7647]

Re: Water in oil but pressure test ok; suggestions?

Was it stored indoors or out side? Have you drained all the oil and put in fresh oil and tried again? If you had it out side being stored you could have got water on the engine that drain down through carb or someplace else. Is there any rust or signs that the top of the engine had water on it.

 

[StevNimrod]

Re: Water in oil but pressure test ok; suggestions?

Pressure tested cold. Even still 15 pounds for almost an hour should show through a crack big enough to get that much water in.

The boat was stored outside with the cockpit cover. No signs of water on top.

Which means that, barring a crack that closes up when it sees 15 psi, the water was put there. Which, if I used the wrong jug of oil (had a cracked block two seasons ago and kept the oil just in case the shop wanted to analyze) and my pump was only pulling out half, I might have put it there myself.

I guess what I'm asking is this: is there any way a mechanical failure (intake gasket, cracked head, block, or intake, or head gasket) will let that much water in the oil NOT show up on a pressure test?

 

[HT32BSX115]

Re: Water in oil but pressure test ok; suggestions?

I guess what I'm asking is this: is there any way a mechanical failure (intake gasket, cracked head, block, or intake, or head gasket) will let that much water in the oil NOT show up on a pressure test?

There's only a few ways that much water can get into the oil.

1. cooling system leaks, (including intake manifold, oil cooler (but only while you have water pressure on the cooler with no oil pressure....)

2. It can "run" in. by being poured in ....Somebody mess'n with you?

3. It can "rain" in over several days of rain. (oil cap left off, leak in via breather pipes/tubes, loose grommet in the valve cover.... etc...)

It came from somewhere.... and it ain't condensation.

 

[StevNimrod]

Re: Water in oil but pressure test ok; suggestions?

Hi Rick,

It seems that I can rule out cooling system leaks, unless you know of a way a pressure test can hold that long with a crack or fault big enough to let that much water in.

It could have been poured in...by me (not paying attention) or someone else.

It's not likely to have rained in - no oil cap was left off, etc.

It seems this might have to be classified as "unknown cause" unless anything else springs to mind.

 

[HT32BSX115]

Re: Water in oil but pressure test ok; suggestions?

Hi Rick,

It seems that I can rule out cooling system leaks, unless you know of a way a pressure test can hold that long with a crack or fault big enough to let that much water in.

It could have been poured in...by me (not paying attention) or someone else.

It's not likely to have rained in - no oil cap was left off, etc.

It seems this might have to be classified as "unknown cause" unless anything else springs to mind.

My next step would then be to drain out as much as possible......it's not gray (emulsified) right?

Change the oil and filter and run the snot out of it! The little bit of water left over will evaporate when it gets hot enough.

While running, stop frequently and check the oil and look for rising level and emulsification(gray/milky etc)

 

[Bondo]

Re: Water in oil but pressure test ok; suggestions?

Or just flush a few times, fill, run hard, and keep fingers crossed?

Ayuh,... Sounds like This is where yer standin'....

Could it have been down the carb, or what about the back from the exhaust thing,..??

 

[solar7647]

Re: Water in oil but pressure test ok; suggestions?

I am on board with the others, clean it and run it. At least that way you know if it is an engine issue or if it got there by you or by weather. You guys did get a ton of snow this year, even covered and buttoned up tight I got snow in my boat during that big blizzard, had to get in with a shovel it out a 50-60mph wind gets snow in anything.

 

[mccrorytr]

Re: Water in oil but pressure test ok; suggestions?

if it is getting in ther after it has been run it could be coming in from the exhaust from a possible cracked upriser.

 

[utexasrick]

Re: Water in oil but pressure test ok; suggestions?

where are you hooking up your pressure tester to. When I was testing mine I initially hooked it up to one of the thermostat outlets and it would hold pressure, then I realized that the thermo valve was still closed. I removed the valve and retested then I could then see a drop off which is what I expected because my oil looked like a milkshake.

 

[StevNimrod]

Re: Water in oil but pressure test ok; suggestions?

I pull the drive and block off the water inlet port at the outdrive bellhousing. Then I remove the hoses on each side that go from manifold to riser (it's a stainless marine exhaust so the water exchange is via hose rather than through passages), plug one and put pressure in the other. At the manifold inlet there's a tee so the manifold is getting water when the thermostat is in any position (open or closed). Also, all of the cooling system hoses get firm when I pressurize it so I'm figuring that I have the whole system from bellhousing through manifolds.

 

[81 Checkmate]

Re: Water in oil but pressure test ok; suggestions?

Sounds like when you didnt do the proper shutdown thing, You had sucked water back into engine and posibly thru the rings into the oil pan???? You stated that you only pulled the plugs and did not drain the oil, so you are not for sure if you had water in oil at that time. I would do an oil change then try again. It also seams that you do not have any slope to your thru hull pipes.

Just my Thoughts!

 

[StevNimrod]

Re: Water in oil but pressure test ok; suggestions?

To update:

The weather finally gave way enough to go out - we ran it for about 40 minutes with no milkshake or rise in oil level.

Which, unfortunately, means that someone put it there. I have a few suspects, myself included :facepalm:.

We did have a problem with it wanting to stumble and die when operated above 3000 RPM. The first time it happened was just after getting up on plane. Then it ran 5 minutes before doing it again. Then it ran 10 minutes before doing it again. Each time I was able to immediately restart it. I'll start another post after doing some tests tonight but I'm thinking it's a fuel delivery issue. Any other thoughts in the meantime?

 

[Bondo]

Re: Water in oil but pressure test ok; suggestions?

but I'm thinking it's a fuel delivery issue.

Ayuh,.... Start with the fuel filters,...
Ya might have some extra water there too...