Milky Oil

FF said:

"I have never seen any engine filled with just water. Manufacturers ALWAYS put in a 50% mix of Anti Freeze and water,"

A new modern engine with a pressure cap needs the 50/50 to raise the coolant boil point.

Many older engines were simply drained overnight and filled when being used again.

A can or 2 of "water pump lube" was added in the spring when draining was no longer required.

Click to expand...

danderer said:

I personally don't think there is much mystery here. I know of 5 or 6 34Ts that have had water in the generator (mine included). The cause was a poorly engineered exhaust system by Mainship. Not enough rise the and vented loop mounted too low.

Click to expand...

gkesden said:

Hey Ross,

It isnt really a specific configuration. It is a common situation on many generator installs. Engine rooms tend to be shallow, so there is just limited headroom. Some boats are certainly more vulnerable than others. The root problem is that pipes let fluids flow both ways and, with boats changing in position in the water, so does the angle that needs to be overcome for things to flow in reverse.

Things can sometimes be improved by raising the elbow or loop vent or the exhaust itself. When I bought my boat, my mechanic went through a bunch of gyrations to raise mine.

The real defense is to run the generator while underway.

Click to expand...

gkesden said:

Hey Ross,

My Kohler 6EOD is a 6KW diesel and it is cooled with a closed loop and heat exchanger versus directly with raw water. So, I am betting yours is the same, even if you are in fresh water. And, if that is the case, I'm really betting on it being a xyz-glycol/water mix. Doing otherwise would just be unusual (and, as I mentioned, in my world, worthy of a cooling system flush and correction).

On your way to the boat what I'd recommend you stop by an auto parts store or Wal-Mart and get an antifreeze tester. They usually cost $4-$9. Something like this:
-- https://www.walmart.com/ip/TESTER-COOLANT-PRESTONE/16817506

Then, once on the boat, I'd pull the cap off of the cooling header tank and look at the inside of the cap and the inside of the neck. Then, I'd put my finger or the corner of a clean shop towel into the tank to get into the fluid. See if there is any oily or milky residue. Oil is lighter than water, so if it gets into the coolant, it'll find its way to the top. Maybe if coolant was getting into the oil, oil was getting into the coolant. If you find oil in the coolant, well, that'll be a big hint (the opposite doesn't disprove anything, though).

The next thing I'd do is give the coolant a good smell. Does it smell like water or antifreeze (or antifree-water mix)? After that, I'd check the coolant with the tester. It basically measures the density of the fluid and can give you a good idea if it is water, coolant, or a mix. It'll also let you see the color. Is it clear like water? Deeply colored like antifreeze? Or lightly colored like a mix?

With luck, your nose, your eyes, and the needle will give a similar (or, at the least, not inconsistent) indication. If you want to be a scientist, you can even send a coolant sample out to be tested, just like the oil. Ultimately, if you've got glycol in the coolant (And, I think you really should), but not in the oil -- I really don't think the coolant system is leaking into the oil.

If you find that your cooling system truly has only water, that's not much help in narrowing things down. So, for the sake of conversation (and, because I think it more likely), let's assume that the cooling system has some glycol -- and your oil sample shows none (as I understand is the case). The question becomes, how can raw water get into the oil?

-- One possibility is that it was over-cranked when starting. In a marine generator if the engine won't start and one keeps trying, the raw water pump can push water through the heat exchanger into the exhaust, and then let it fall back into the motor This is actually a pretty dangerous condition, because it can get into the cylinder and cause a hydrolock with damage like bend rods or much worse. Basically, unlike a fuel-air mix, the cylinders can't compress water, so if the generator starts and it tries, things bend and break. (If a genset won't start after a short attempt, close the intake seacock, until it does...)

-- Another situation that can cause a hydrolock in an aft-exhaust genset is cruising without the genset running. If one backs down or gets hit with following seas, without the positive pressure from exhaust, it is possible for water to get forced up the exhaust and for the same thing to happen. (This is why I always cruise with my genset on and had the exhaust and elbow raised higher.) The same can happen with side exhaust from excessive rocking side-to-side when moored or anchored. (In a badly designed exhaust, shared with the main(s), the main(s)'s exhaust can also get pushed backward into the genset).

-- Another possibility is that a human was intending to top off the coolant -- and dumped it into the valve cover cap, instead. It sounds crazy. But, depending upon access, it may be easier to do than it seems. They are often similar-sized push-and-twist caps on top.

-- If the generator has an oil cooler, it could be leaking. I think it unlikely. My last generator didn't have one. And, on my current generator it is a rarely installed option. If you can tell me the model of your generator, I can see if I can find the service or parts manual and look.


As you can probably tell from some of my posts, I am the type that likes to collect all the data first. So, although I'd change that oil and filter repeatedly right away. I'd also have sent it off for analysis (as you did), analyze the coolant (sending it out, if needed), think carefully about the usage and service history for clues (hard start? following seas while off? Recent fill with coolant?) and look carefully for signs of raw water backing up, rust, etc.

At any rate, if you post the model of generator, I can google around and see if I can find the service and/or parts manuals, and see if there is likely an oil cooler or not.

But, I think the absence of glycol in the oil will turn out to be a big clue.

Cheers!
-Greg

Click to expand...

danderer said:

This is the vented loop on my boat. Note it is as high as it can go in the ER. When Mainship built the boats they placed them about 10" lower.

There was also no rise between the muffler and the overboard discharge. My new configuration has some rise there as well.

This exhaust system for the generator is completely separate from the one for the main engine. The main engine shouldn't have this problem - the muffler on that engine has a 'overflow' port on it that leads overboard. If the water gets too high in that muffler it drains through that port.

Click to expand...

rgano said:

With my boat in a fixed orientation in its wet slip, I have simply plugged the exhaust port with a rubber plug until I can get it out of the water again on its repaired lift. I never would worry about it at anchor where the waves would not be consistently hitting it broadside as they can do now.

Click to expand...

gkesden said:

Hey Ross,

Cranking for a couple of minutes can be plenty long enough to get raw water into the engine. You may have actually gotten lucky that nothing had a bad day as a result (and the same is true if it came in via the exhaust).

In the future, if you ever find yourself needing to crank for a while, even across multiple bursts, close the intake seacock first, then open it immediately as soon as the engine starts. And, of course, be careful about over heating the starter. They can handle tons of current in short bursts -- but need time to cool off in between or they'll burn up.

People seem to have very different experience with the flaps. You'll have to think through your configuration from exhaust discharge back to the genset and mentally estimate how likely it is that water pushed its way past them and up into the exhaust given the seas and how the boat was operated.

Given that flaps are there, and the history of extended cranking, I'm betting on it being the extended cranking. But, it doesn't really matter. Do what you can to raise the exhaust, if you can. It'll be safer that way. And, you already have flaps, for whatever they are worth. Beyond that, I'd suggest using safest practices, such as running the generator any time you are cruising and closing the seacock (and letting the starter cool) during extended cranking. (Note: I avoided using the phrase "best practices", because I know others feel differently about the need to run a genset while cruising. But, I suspect we can all agree, at the least, it is the most conservative practice.)

If you find the model of that generator, I can google it for you and see if I can find a parts or service manual. If, like mine, it has no oil cooler -- that would scratch that off the list and basically strongly point to it being from the exhaust or raw water pump.

Cheers!
-Greg

Click to expand...

Ski in NC said:

Do not worry too much at this point how the water got in. Focus on getting the water out of the oil for storage.

There is no oil cooler on these to leak, and the head gaskets are reliable. And the sample did not indicate glycol. So it is likely an issue with siphon break and/or exhaust issue. None will be a problem in runs needed to dry out the engine.

Raw water pump is belt drive, so that is off the list too.

Click to expand...

Lou_tribal said:

One advice when checkin the oil, check also the level for anormal high level. Water separate from oil and oil float on water. If oil is clean but higher than last time you check that may be oil floating on a layer of water...

Click to expand...

gkesden said:

Hey Ross,

Ever siphoned water from an aquarium into a bucket? Or from a vehicles fuel tank into a portable tank?

Basically, imagine a situation where the are two buckets "High" and "Low". If directly connected, such as via a drain hose, "High" will naturally drain by gravity to "Low". As gravity pulls water from "High" down into "Low", air is easily displaced into the high bucket and out of the low bucket to conserve volume. Easy peasy. We see this all the time.

Now imagine exactly the same buckets, and exactly the same gravity, except that, instead of the drain connecting directly from the bottom of the "High" bucket, it is a hose that reaches the bottom of the bucket before going above the bucket and then looping down into the "Low" bucket.

The water in the "High" bucket still has more potential energy than the water in the ow bucket. Gravity still wants to pull it down. But, it doesn't have a source of energy to get pulled up the hose farther so that gravity can take it from there. So, the water stays in the high bucket.

Now, imagine that we use suction to fill the hose with water, pulling it from "High", into the hose, filling the hose. Now two things happen. The first is that the "pulling" of the water from "High" into "low" generates a low pressure area in "High", which in turn pulls water into the hose. Essentially, atmospheric pressure is now pushing water up over the hump, so gravity can pull it down. Also imagine that, like links of a chain, the water molecules are attached to each other, admittedly quite weakly, because they are dipole molecules and the polar bonding causes cohesion. Now we have a situation where a combination of atmospheric pressure and the tug of one molecule of draining water upon the next one in line keeps water flowing from "High" to "Low". The combination of these two forces causes the siphon effect that we know an love -- given enough height difference, enough initial suction, a compatible hose volume, little enough friction, etc, etc, etc once the water starts moving from "High" to "Low", it'll keep flowing.

So, how do we stop this from happening One thing we can do is put a valve at the high point of the hose that, in the event of negative relative pressure (suction), opens up and lets air into the hose. This air is sucked in at or near the top. So, as the water is pulled down, it is air, not more water, that displaces it. Now the hose fills with air as the water falls rather than pulling more water by suction or cohesion, so the "siphon is broken".

How can suction pull water into an exhaust? One way is that it can mechanically get started and then just keep on going. Another way is that as an engine is cooling, the gases cool off and take up less space. And, this generates suction. Add mechanical events and suction from cooling and water can get where you don't want it. A siphon break helps with both.

You don't really want it below the water line, or it, itself, can be a leak water from the outside in. The flapper isn't intended as a seacock. So, for best performance and safety, you normally want them at the apex of the loop decidedly above the water line in any condition. Too high and it becomes an impediment to legitimate water travel (pump head to get started, friction, etc).

As for belt driven raw water pumps being unable to fill an engine with water -- I do not believe that is generally true. The turning of the impeller moves water. It doesn't really matter if this impeller is turned by the auxiliary (accessory) gear or by the auxiliary (accessory) belt. In most engines, the gear or belt turns any time the engine does. This includes it getting turned by a ratchet ("barred over"), getting turned by the starter, or getting turned by normal operation. The alternative would require something like a clutch to disengage the auxiliary driver or belt until the engine is started -- and that just isn't common on recreational vessel mains and generators.

Having said that, I still don't know which generator you have. And Ski seems to know that it has no oil cooler and a belt-driven raw water pump. So, he may know a heck of a lot more than me about your generator, in particular. And, it is definitely true that different generators are at different levels of risk of this type of thing. So, if he knows yours, he may know that.

What ski meant by "none will be a problem in runs needed to dry out the engine" is that whatever initial conditions (long start or exhaust backup while not running) caused you to get the water in the oil originally won't be the case during a test run in which the engine starts up and the generator is running.

What he is suggesting is that since there is no oil cooler or anything else to fix, the best thing you can do is get it flushed out really good by running it. And, to do that, you don't need to do any more research. Just do it sooner than later to prevent corrosion.

Click to expand...

RossWilson said:

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.

Click to expand...

JoeApicella said:

Any mechanic should know milky oil is caused by water emulsified in the oil. In the very least, drain all the oil out even if you have to leave it empty over the winter. If you can run it then put in fresh oil and filter, start it briefly then check to make sure it is clear. In the spring I would run it and change the oil and filter again.

Click to expand...

Mark Laurnen said:

All advice has been spot on ... that oil should come out. I was in a similar situation with a gas V8 in a jet boat that nearly sunk. I am sure that motor had a water load much greater than yours. After several oil changes still showing water contamination, I drained the motor, changed the filter, and filled it with kerosene to the top. It was some time before I could drain the and kerosene replace the oil/filter. No apparent harm was sustained through this unfortunate episode. As a back up plan, if you can’t run your engine while it is in storage you could pickle it with any light oil, diesel, or kerosene. It will just take another couple of oil changes to clear that out in the spring. With all of the preceding sage advice, you probably know more than your mechanic ... I’m sure you are smarter.

Click to expand...

Les_Garten said:

I don't know who you been talking to, but one thing is for sure, he ain't no mechanic...

Click to expand...