1992 OMC 351 King Cobra

[300sflyer]

Hey guys, went to change the oil in a friends boat, and the level is twice as high as it should be... Sucked the oil out and it is all milky... Strange thing is there are no external leaks anywhere on the engine when running it on the muffs. Lots of water coming out the exhaust. Do these things only crack internally if they froze? I would have expected some external leaks too!

Thanks!

 

[Scott Danforth]

many times they do leak internally, or the thermostat housing busts out of the bottom of the intake manifold.

pressure test to find where its leaking.

 

[southkogs]

There are a few ways to get water into the oil. Is there signs of water in the bilge? Compression issues? Any water circulation issues?

 

[300sflyer]

There was some water in the bilge, but nothing serious. We had heavy rain here over the weekend, so that could account for it. I have not done a compression check, or a cooling system pressure test. Its always been a freshwater boat, so I would not suspect anything has rusted out.

 

[HT32BSX115]

We had heavy rain here over the weekend, so that could account for it. I have not done a compression check, or a cooling system pressure test.

Howdy,

When was the boat operated last? (If last summer....... it's most likely a cracked block from improper, or lack of winterization......meaning the block was not drained)


Heavy rain would only allow water into the crankcase if there was an obvious entry point.

if you think the water got in from rain etc......your best bet will be to drain all the water out using suction or draining at the bottom of the pan if possible.

Then run the engine (meaning run on the lake to get it up to normal cruising speed and operating temp) .

You may have to change the oil a couple of times to get it all, allowing it to completely warm up each time to get remaining water to emulsify so you can drain/suction it.

Some people will also use a quart of diesel/kerosene in the oil (to thin it) so as to speed the emulsification so as to drain it easier.

I don't like doing that. I would just use some thin (when cold) oil like 5W-20 or 5W-30 to get any remaining water (to mix) that you cannot drain first.

A compression check will not usually reveal a cooling system leak (unless it's a head gasket but head gaskets do not always result in water in the oil ) .

You MUST pressurize the cooling system to find block cracks.

Water in the oil is almost always a cracked block where the cracks are internal. Blocks don't always crack on the outside.

If the cooling system holds pressure, then the water got in there from some other point. But rule out a cracked block first since a cracked block will mean engine replacement.

Cheers,

Rick

 

[300sflyer]

Just pressurized the cooling system, and tapped into the main water supply hose, before the engine oil cooler to rule it out as well. 14 PSI and 20 minutes later, it's still holding.... Now I'm really puzzled as to how all that water got in the oil pan? Must have been almost 4 litres of water in there.

 

[Scott Danforth]

do you have rust trails down your exhaust manifold from the riser joint? if the block is holding pressure, then i would suggest inspecting the manifolds and elbows.

 

[300sflyer]

I was thinking manifolds too, but then I cant imagine that much water getting into the crankcase that way. My friend just bought the boat, and does not have a good history on it.

 

[HT32BSX115]

I was thinking manifolds too, but then I cant imagine that much water getting into the crankcase that way. My friend just bought the boat, and does not have a good history on it.

It's very hard to get very much water from the manifolds into the crankcase......

But if your cooling system held 14 psi for 20 min you can sort of breathe a sigh of relief!!



I would drain the emulsion, try to get as much out as possible and fill with clean oil and run it (fairly hard)

Get it up to normal temp and check the oil. If it's still milky, (and it might be,) plan on another drain/fill.

If might take a couple of times to get rid of most of the residual water. Once you get it to only a little water, it will evaporate out if you run it at normal operating temp for an hour or 2.

My guess it that it sat in the rain with water running on top of the engine that somehow got in to crankcase from above.

I would still remove the manifolds and risers to inspect/replace the gaskets. You can look inside the risers and manifolds for rust tracks inside. If they're questionable, cracked or leaking, you need to replace the entire mess. (an exhaust/riser kit is usually around $600 or so....maybe more for FOMOCO engines)

 

[300sflyer]

The exhaust manifolds and risers look good on the outside. There are no rust stains. After the third oil and filter change, the oil looks good again. Running the engine on muffs, did not add any water to the oil. Hopefully it stays that way...

One thing I did find missing after the first oil change was the thermostat. The engine would heat up at all... it now has a 160F in there and seems good now.

Time for a good run out on the water.

 

[HT32BSX115]

The exhaust manifolds and risers look good on the outside. There are no rust stains. After the third oil and filter change, the oil looks good again. Running the engine on muffs, did not add any water to the oil. Hopefully it stays that way...

One thing I did find missing after the first oil change was the thermostat. The engine would heat up at all... it now has a 160F in there and seems good now.

Looking "good on the outside" is not a very good "test", also, if your block is cracked, you won't always get water in the oil using "Muffs"......

Time for a good run out on the water.

Yup. That will be your acid test.

Good luck!