Milky oil in Starboard engine - 2 454's (mercruisers) v-drives. Closed cooling with oil cooler

Beech2000

Beech2000

Active Member
Jul 11, 2015
250
NW Georgia USA
Boat Info
1990 Sundancer 350
Engines
2020 454 gen VI
Hurth V-Drive's
7.1 KW Kohler 5ECD
Starboard engine our 90 Sea Ray Sundancer continually has on going milky looking oil. Two oil changes since last February, 110 hours now have accumulated with no operational issues. Still the same creamy looking oil noted. Today a third oil change. Closed cooling antifreeze level stays normal, antifreeze has normal lime green appearance with no external leaks.
Since no external leaks and no antifreeze loss that I can tell in closed cooling, guessing I'm dealing with lake water intrusion from somewhere...... Intake manifold gasket? Cracked head? Cracked block? Exhaust riser ???
Oil appears thick and lubricity seems normal. No operational temperature at all. Not suspecting large intrusion just annoying discoloration and loss of sleep for same. Thoughts?
 
We have ‘91, same combination. Things to consider; is oil level growing, is there any oil sheen in exhaust water, is operating temp normal, does engine start and run normally with no missing. My first look would be engine oil cooler. I think there is no way raw water can get in crank case otherwise. Entire engine is cooled by antifreeze
side, so if leak at block,antifreeze side level would change. Good luck and keep us posted of findings.
 
Oil coolers
The water flows though the oil cooler to cool the oil, I have seen the oil cooler go bad and mix the water and oil.
 
Beech2000 said:
Starboard engine our 90 Sea Ray Sundancer continually has on going milky looking oil. Two oil changes since last February, 110 hours now have accumulated with no operational issues. Still the same creamy looking oil noted. Today a third oil change. Closed cooling antifreeze level stays normal, antifreeze has normal lime green appearance with no external leaks.
Since no external leaks and no antifreeze loss that I can tell in closed cooling, guessing I'm dealing with lake water intrusion from somewhere...... Intake manifold gasket? Cracked head? Cracked block? Exhaust riser ???
Oil appears thick and lubricity seems normal. No operational temperature at all. Not suspecting large intrusion just annoying discoloration and loss of sleep for same. Thoughts?
Click to expand...


There are a couple of tests that can help you sort it out. First, I would do a pressure test on the cooling system to see if it holds pressure. Within a couple of minutes you will know if the cooling system (antifreeze) is compromised. The great part of having two engines is that you can compare results between the two. To do this test, you need this device:
https://www.amazon.com/Mityvac-MV4560-Radiator-Cooling-Pressure/dp/B003V9L05G
61HFEPxqA6L._SL1000_.jpg



The next test which is equally easy is to have the oil tested by these folks:

https://www.blackstone-labs.com/pro...abs.net/Bstone/(S(eq2ioaqnzbqqa145grzvxr55))/

The lab test ($30) will tell you what is in the oil. If it confirms water and not anti-freeze then one of your heat exchangers may be compromised. By this point though....most of your exchangers should have been replaced since they barely last 20 years.
 
If I were you I'd replace both oil coolers and trans coolers. It's cheap insurance and both probably need to be replaced at this point. Trans coolers are easy DIY. I'm not so sure on oil coolers.

Mrcool is a great place for high quality, low cost parts. Highly recommend...and made in Michigan :)
 
How's a bad HE going to leak water into his oil ? Not goin to happen. Usually when a HE fails the antifreeze under 13 lbs of pressure gets forced out with the raw water flow.
I'd bet on the oil cooler.
 
scoflaw said:
How's a bad HE going to leak water into his oil ? Not goin to happen. Usually when a HE fails the antifreeze under 13 lbs of pressure gets forced out with the raw water flow.
I'd bet on the oil cooler.
Click to expand...

I had a heat exchanger fail on a trans cooler and the water ended up in the trans. Maybe not what you were talking about?
 
PlayDate said:
There are a couple of tests that can help you sort it out. First, I would do a pressure test on the cooling system to see if it holds pressure. Within a couple of minutes you will know if the cooling system (antifreeze) is compromised. The great part of having two engines is that you can compare results between the two. To do this test, you need this device:
https://www.amazon.com/Mityvac-MV4560-Radiator-Cooling-Pressure/dp/B003V9L05G
61HFEPxqA6L._SL1000_.jpg



The next test which is equally easy is to have the oil tested by these folks:

https://www.blackstone-labs.com/products/free-test-kits/?session-id=eq2ioaqnzbqqa145grzvxr55&timeout=20&bslauth=&urlbase=https://www.blackstone-labs.net/Bstone/(S(eq2ioaqnzbqqa145grzvxr55))/

The lab test ($30) will tell you what is in the oil. If it confirms water and not anti-freeze then one of your heat exchangers may be compromised. By this point though....most of your exchangers should have been replaced since they barely last 20 years.
Click to expand...


You can borrow this and a lot of other tools from Advanced Auto Parts (and probably others). I'd sample the oil and get a read on that first. Antifreeze would leave a tell tale chemical signature.

I'm thinking oil cooler.
 
scoflaw said:
Trans cooler is similar to an engine oil cooler not a HE.
Click to expand...

Just curious....why are you splitting hairs on this? A trans cooler and oil cooler both transfer "exchange" heat with raw water just as a closed system does.

I would think before I replaced any parts that I would at least check the history on the components and test the system.

The other point is that I have yet to see an engine oil cooler fail. The pressure differential would suggest that the oil side is at .....let's say 1000 rpm is 40psi. The raw water side is at best 5 psi at the same rpm. If oil was going anywhere.....it would be leaking from the engine into the raw water and the amount of oil in the engine would be less.

Just my thoughts.
 
PlayDate said:
Just curious....why are you splitting hairs on this? A trans cooler and oil cooler both transfer "exchange" heat with raw water just as a closed system does.

I would think before I replaced any parts that I would at least check the history on the components and test the system.

The other point is that I have yet to see an engine oil cooler fail. The pressure differential would suggest that the oil side is at .....let's say 1000 rpm is 40psi. The raw water side is at best 5 psi at the same rpm. If oil was going anywhere.....it would be leaking from the engine into the raw water and the amount of oil in the engine would be less.

Just my thoughts.
Click to expand...
I have 100 % seen oil cooler go bad and the oil get milky on my friends boat, he had a mechanic change the oil cooler and the oil 6 times and the problem was fixed
 
Spark600 said:
I have 100 % seen oil cooler go bad and the oil get milky on my friends boat, he had a mechanic change the oil cooler and the oil 6 times and the problem was fixed
Click to expand...

That is interesting.....seems to go against the pressure dynamics unless the engine had really low oil pressure.
 
PlayDate said:
That is interesting.....seems to go against the pressure dynamics unless the engine had really low oil pressure.
Click to expand...
Not sure, but I think I remember him saying something to do when the motor was shut done. Not sure
 
PlayDate said:
would suggest that the oil side is at .....let's say 1000 rpm is 40psi. The raw water side is at best 5 psi at the same rpm. If oil was going anywhere.....it would be leaking from the engine into the raw water and the amount of oil in the engine would be less.

Just my thoughts.
Click to expand...

It’s a result of the Venturi effect. Much like a foam educator.

Send high pressure liquid (motor oil) down a tube and it will suck in liquid (sea water) as it passes a small orifice, even though the liquid (sea water) is at a lower pressure.

If the 2 liquids of different pressures were static and not flowing, then you would see the higher pressure liquid flowing into the lower pressure area.
 
Last edited:
Espos4 said:
It’s a result of the Venturi effect. Much like a foam educator.

Send high pressure liquid (motor oil) down a tube and it will suck in liquid (sea water) as it passes a small orifice, even though the liquid (sea water) is at a lower pressure.

If the 2 liquids of different pressures were static and not flowing, then you would see the higher pressure liquid flowing into the lower pressure area.
Click to expand...

That would be an interesting experiment. While I agree that Venturi effect could theoretically play a role in some problems I struggle to see how it fits an oil cooler.

The cooler is pressurized between 40-60 psi with 3/8 oil lines. Poke a hole in it and it will send oil across the room if the engine is running. I'm willing to bet that at idle when most raw water pumps are only capable of 1-2 psi having 40 psi on the other side would not create a venturi effect and if it was leaking .....you would see oil in the raw water exhaust. At higher rpms....that could be a different story.

I had this debate last year on offshoreonly.com with a go boat owner and he was convinced it was the cooler.....a compression test/leak down test showed that his head gasket was leaking.

Anyway....it is a moot point until we get some more data. Getting the oil tested will point if it is antifreeze or water in the oil.

Also taking some of it out of the engine and letting it sit may also lead to an obvious answer.
upload_2020-3-7_14-20-48.png
 
PlayDate said:
That would be an interesting experiment. While I agree that Venturi effect could theoretically play a role in some problems I struggle to see how it fits an oil cooler.

The cooler is pressurized between 40-60 psi with 3/8 oil lines. Poke a hole in it and it will send oil across the room if the engine is running. I'm willing to bet that at idle when most raw water pumps are only capable of 1-2 psi having 40 psi on the other side would not create a venturi effect and if it was leaking .....you would see oil in the raw water exhaust. At higher rpms....that could be a different story.

I had this debate last year on offshoreonly.com with a go boat owner and he was convinced it was the cooler.....a compression test/leak down test showed that his head gasket was leaking.

Anyway....it is a moot point until we get some more data. Getting the oil tested will point if it is antifreeze or water in the oil.

Also taking some of it out of the engine and letting it sit may also lead to an obvious answer.
View attachment 80583
Click to expand...

I see your point. The pressures could be a little low for a proper Venturi effect. We use 200psi for foam. This scenario has lower pressures and smaller pressure differential.
 
I'm headed down to lake today. I have a radiator pump. Told by several people the oil coolers are notorious for water in oil. I'll be purchasing replacements this week. Thanks all
 
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