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Old 11-01-2019, 07:02 AM   #1
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Milky Oil

Hello Everyone:
When the marina mechanic was changing the oil and filter on my diesel generator recently, he found that the oil was the colour of cafe au lait, that is to say, coffee with cream.


He offered no immediate opinion as to the cause, but advised an oil test. I agreed and he continued with the service. A couple of weeks later, after the boat had been hauled and stored in a heated building for the winter, I received a message from the service manager stating that the milkiness was the result of water in the oil. (BTW - my boat is a fresh-water vessel.)



He suggested that the water probably entered as a result of cranking the genny without starting it. I had been having difficulty starting it a month or so earlier due to a weak battery and never got it started before hauling. He recommended that I start the generator after launch next spring and let it run for an hour or so, and that should resolve the water issue.



Now after another month, I'm wondering if that was good advice. It seems to me that changing the oil once probably won't remove all traces of the water. And leaving it in the genny all winter couldn't be good for the engine. If this is true, what should I do? Any other options? Should I change the oil and filter again before running it in the spring? Should I insist that the oil be changed again now even though the boat is on-the-hard? Thanks.
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Old 11-01-2019, 07:21 AM   #2
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Letting milky oil sit in your generator over the winter will let the water evaporate a bit on warm days and condense under the valve cover, often causing rust on the valve train. Also milky oil isn't doing as good lubricating the internal parts when it is running, but that is moot for the winter.

Even though you may not be able to run it long now, I would change the oil at least once. Then start it and let it run for a minute or so to circulate clean oil through the engine. It won't hurt it to do so with no raw water supply for just a few minutes.

I don't think your mechanic did you any favors by waiting until he got the oil sample tested and the boat was hauled for the winter. Milky oil is milky oil and it was bound to show water in the oil test.

In the spring watch it closely and if it returns it could be something like a blown head gasket. Did the test show antifreeze in the oil?

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Old 11-01-2019, 08:18 AM   #3
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My genny (three cylinder Yanmar) was full of water when I bought the boat. P.O. reduced the price by $5,000 saying it was either a blown head gasket or a cracked block. It still ran fine. Three different Yanmar mechanics told me "Yanmars don't blow head gaskets or crack blocks) PERIOD. A fourth mechanic actually went into the bilge and did some exploring. He found three separate problems which could have caused the engine to "sip seawater".

I changed the oil and then filled it with used oil from my F.L. (about 80 hours on it) ran it and drained it again, still milky. Filled it again, used oil again, ran it and drained it, getting better. (changed filter every time.)

It took between 5 and 10 oil changes but it is finally clear. BTW, when running the genny , I would notice a kind of "ammonia" smell in the bilge. I generally don't run the genny for long periods, maybe a couple hours at a time. It turned out that the breather was exhausting into the bilge and not into the air intake on the engine. Since there was still some water in the oil there was still quite a bit of steam coming from the breather.

Problem solved! Don't automatically assume your engine is "hatched" because the oil is milky.

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Old 11-01-2019, 08:24 AM   #4
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Greetings,
Mr. RW. I fully agree with Mr. dj. Get that oil out of the genny now. Change the oil and crank it over for as long as you can without damaging the starting system (starting motor/battery cables).



Start looking for another mechanic as well. Milky oil always means water/antifreeze in the oil. That's a no-brainer. Oil analysis? Waste of $$, at this point IMO. Water is water and I know no other cause of milky oil. He should have drained and changed the oil immediately.
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Old 11-01-2019, 08:46 AM   #5
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Yea, you don't want that engine sitting over the winter with water in it. Good chance you will be buying an engine in the spring.

What generator model/brand?

I'd get the yard to back the boat out of the shed to where you can do a proper job of drying out the engine running it loaded on garden hose.

If that is too much trouble, might be able to fill whole engine with oil or diesel. Maybe take rocker cover off and dry out that area, that's where condensation tends to collect.
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Old 11-01-2019, 09:32 AM   #6
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Thanks, David, for your reply and advice. I've still not received a copy of the oil test results. All I got from the service manage of the marina is the following message:


"I have attached the results of the oil analysis shows a high level of water in the oil. The generator is closed cooled which means it has a heat exchanger and has no water near the engine. One way water can get ingested would be over cranking the engine without it starting. This would cause sea water from the pump to build up in the muffler and could back up into the engine making its way into the cylinders and ending up in the oil. I would recommend running the engine in the spring for at least an hour or two then changing the oil again to get out any remaining water, this will also give an opportunity to check if more water is intruding into the oil. If no more water is shown in the oil then I would monitor the engine oil though out the season by checking it after running it."


My boat has been in a heated building on site for the last month or so. And the oil and filter were changed early September. But to my knowledge, the genny has not been run since then. I don't know if there was any antifreeze in the oil test report. I guess I don't trust the service manager, or maybe even my current marina. Actually, I plan to leave them in the spring.
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Old 11-01-2019, 09:38 AM   #7
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Thanks for your comments, Pete. My generator is a Kohler 8kw diesel with fewer than 100 hours. Still unsure what to do, but not being terribly mechanical, I'll contact the service manager again to seek a solution. At least with all you guys offering the benefit of your combined experience, I'll have the questions to ask.
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Old 11-01-2019, 09:44 AM   #8
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Thanks, RTF. Fortunately, he did change the oil and filter on the day it was discovered the problem. But only once. And he didn't run it and check the oil again.



But now the boat is inside and on blocks with batteries disconnected. What can I do now except await spring launch? Or can the engine be run, followed by another oil and filter change? The service manager said it's close-cooled with a heat exchanger. Does this mean it can be run without being in the water?
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Old 11-01-2019, 09:44 AM   #9
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What Ski said. Have the yard drain the oil and run the engine until warm using a garden hose for the raw water. Let it warm up good under load. Drain and refill again. This time with a new filter. That will get you through the winter. Monitor in the spring. Maybe need to repeat another time or two in spring. No worries especially with fresh water in the engine.
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Old 11-01-2019, 09:48 AM   #10
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Quote:
Originally Posted by Ski in NC View Post
Yea, you don't want that engine sitting over the winter with water in it. Good chance you will be buying an engine in the spring.

What generator model/brand?

I'd get the yard to back the boat out of the shed to where you can do a proper job of drying out the engine running it loaded on garden hose.

If that is too much trouble, might be able to fill whole engine with oil or diesel. Maybe take rocker cover off and dry out that area, that's where condensation tends to collect.
It's a Kohler 8kw diesel generator. And my boat is sitting in the back corner of a very large building with probably a half dozen other large vessels blocking the exit. So, she's not going anywhere 'til spring. Now I'm really concerned. Time to have a serious chat with the manager. Thanks for your advice.
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Old 11-01-2019, 09:50 AM   #11
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Quote:
Originally Posted by Cigatoo View Post
What Ski said. Have the yard drain the oil and run the engine until warm using a garden hose for the raw water. Let it warm up good under load. Drain and refill again. This time with a new filter. That will get you through the winter. Monitor in the spring. Maybe need to repeat another time or two in spring. No worries especially with fresh water in the engine.
Thanks for your comforting advice. All I need now is the cooperation of the service manager who is probably overloaded with work due to the pressure of having to get all their boats out of the water before the cold weather arrives.
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Old 11-01-2019, 09:51 AM   #12
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I bet it wouldn’t be the first time if they found a way to run it inside. Where there is a will there is a way.
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Old 11-01-2019, 10:14 AM   #13
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Greetings,
Mr. RW. To potentially cover your butt for the future it may be of some benefit to send a registered letter to the service manager outlining the whole story and exactly what the yard did and did not do AND your concerns about leaving moisture in the engine for 6 months. Any problems that develop over the next few years that can be traced to the yard's incompetence might put them on the hook for any repairs/replacements. 100 hours is a new unit. Keep a copy for yourself and proof of registration, of course.

IF any problems develop, you then have the incident on record and IF litigation is necessary it won't be a case of he said/I said. Just a thought.


Don't take any heed of anything the manager says now. He may be as lame as the mechanic.
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Old 11-01-2019, 10:20 AM   #14
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If you over cranked the engine enough to back water into the engine from the exhaust, you would most likely have hydrolocked the engine and the engine would not crank. It takes very little water coming in an open exhaust valve to hydrolock that cylinder. I think that is a very unlikely way to get water into the oil. The only other ways that you can get water are failed seals on a gear driven raw water pump, a blown head gasket or a failed oil cooler. A bad head gasket would put antifreeze in the oil while a bad seal on a gear driven raw water pump would put salt water into the oil. What a failed oil cooler puts into the oil depends on how it is plumbed. The oil analysis should tell you if you have antifreeze or salt water in the oil.


I second firing that mechanic.
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Old 11-01-2019, 10:38 AM   #15
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The generator can be run for a few minutes without hooking up water to it. It won't overheat because the coolant system takes a while to heat up. So the engine will be fine. The exhaust hose needs raw water to protect it from overheating, but as long as you don't put any load on the generator the exhaust will be cool enough as will take a while for the head and exhaust manifold to heat up enough to harm the exhaust hose.

The only thing that could be damaged from running for a few minutes without water is the pump impeller. You can either remove the impeller beforehand or just check and replace it in the spring.

Running the engine will circulate the new oil through the oil passages and bearings and push out the remaining milky oil. You said the mechanic changed the oil when he noticed the milkiness but did not run it afterwards. That was dumb if it still was in the water. So run the engine for a minute or two, change the oil and run it again and you should be ok for the winter.

But check the oil after running for a few minutes and see how it looks.

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Old 11-01-2019, 10:41 AM   #16
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Quote:
Originally Posted by RT Firefly View Post
Greetings,
Mr. RW. To potentially cover your butt for the future it may be of some benefit to send a registered letter to the service manager outlining the whole story and exactly what the yard did and did not do AND your concerns about leaving moisture in the engine for 6 months. Any problems that develop over the next few years that can be traced to the yard's incompetence might put them on the hook for any repairs/replacements. 100 hours is a new unit. Keep a copy for yourself and proof of registration, of course.

IF any problems develop, you then have the incident on record and IF litigation is necessary it won't be a case of he said/I said. Just a thought.


Don't take any heed of anything the manager says now. He may be as lame as the mechanic.
That would light a fire only if the yard and mechanic are working together. If the mechanic is independent, the yard has few worries about the matter.

There are ways to run a garden hose to the intake or plumb in a garden hose into the cooling line temporarily and use a tapered rubber plug to catch the outflow and run the wastewater back out of the building, which would be simpler than removing the boat in the back corner.
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Old 11-01-2019, 10:49 AM   #17
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I would want to find a way to run it and then change the oil and run it again. Then look at the oil and see if it is still milky. I would hate to ruin a 100 hour old generator.
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Old 11-01-2019, 10:49 AM   #18
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I would take the belt off of the raw water pump and run it for a couple of minutes to circulate the oil around, change it and repeat. They probably run the boats in and out of the shed with a diesel travel lift, so I don't see a big difference between that and running your generator for a couple of minutes. I can see where they would want to discourage it, but seeing how it should have been addressed by their service staff properly and there is no real hazard, they should be amenable to this.
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Old 11-01-2019, 10:50 AM   #19
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All good advice. For the unwary, do not unnecessarily "over crank" your engine when boat in water unless raw water valve closed.
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Old 11-01-2019, 10:59 AM   #20
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The hazards of running an engine dry are ruining your raw water impeller, overheating your engine or overheating your exhaust system because there is no water running through it. All of which can be mitigated by disconnecting the raw water belt and keeping an eye on the temps. It is good to be knowledgeable of the constraints before speaking with the boatyard so they can't talk you in circles.
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