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windmist 03-11-2015 12:57 PM

Water in Transmission Oil
I decided it was time to change the transmission oil in my new to me boat. The oil came out brown and sure looks like water is in it. :banghead:

The engine is a Cummins 6CTA8.3 M3 - 450 HP with a Twin Disc MG 5075 transmission.

Any ideas where I should look for the problem? Thanks

Larry M 03-11-2015 01:00 PM

Oil cooler, if it has one, may have failed.

Alaskan Sea-Duction 03-11-2015 01:03 PM


Originally Posted by Larry M (Post 315581)
Oil cooler, if it has one, may have failed.


No Mast 03-11-2015 01:42 PM

Agree, it should have an oil cooler and thats where you should expect to find the leak.

After you replace the oil cooler, I would suggest two more oil changes to get all the water out. I would do the first after maybe an hour, and the second after 3 to 5 hours perhaps.

Marin 03-11-2015 01:47 PM

While the suggestions above are probably correct, keep in mind that as ATF (if your transmission uses ATF) gets old, dirty and worn out it begins to turn brown.

No Mast 03-11-2015 01:48 PM

Come to think of it that's the engine in our boat. It should have a zinc on the aftercooler and the heat exchanger, have you checked or replaced them?

I believe some after coolers had two zincs for some reason, but I could be mistaken. My wife claims I frequently am.

Maybe all this is obvious, but coming from the sailboat world, I was surprised to find zincs inside the boat.

windmist 03-11-2015 01:50 PM

Thanks all. Is there a chance I've done damage to the tranny? I don't know how long water has been in the oil. Shame on me, but I seldom check the tranny oil. When I did check the dip stick, before pumping out the oil, there was a lot of pressure as the brown liquid spit out the tube when I pulled out the dip stick. My first clue I was in trouble.

windmist 03-11-2015 01:52 PM


Originally Posted by Marin (Post 315597)
While the suggestions above are probably correct, keep in mind that as ATF (if your transmission uses ATF) gets old, dirty and worn out it begins to turn brown.

I wish, but this Twin Disc uses regular 30 wt oil.

No Mast 03-11-2015 01:55 PM

To Marins point, you can test to see if there is water in it or not. Of course you can have it analyzed, but you can try #2 in this link:

Poor Man's Oil Analysis - The Motor Oil Evaluator

I've done it with just a match before.

As I write this, if the boat is new to you, having the oil analyzed can be a good source of knowledge on the health of the power plant and trans.

Larry M 03-11-2015 01:57 PM

Call Mike at Harbor Marine in Everett. He's probably the West Coasts most knowledgeable transmission guy plus he'll talk to you on the phone. (425) 259-3285

Marin 03-11-2015 02:01 PM

Has the oil just turned brown? If you checked the transmission oil level prior to the last time you ran the boat, was it a "normal" color?

No Mast 03-11-2015 02:07 PM

Google water in engine oil and look at the images results. many pictures so you can compare what you're seeing.

If it is water it has a milky appearance. If it has a lot of water you can also have bubbles I think.

sunchaser 03-11-2015 02:27 PM

Sorry about your issue Windmist. As noted by Larry, you are in a good place to have some top notch help troubleshooting the transmission.

For any newbies out there this is an important post. Transmission coolers are relatively cheap and after a cleaning or two many consider them throw away items. Secondly, fluid checks should be done before the days's cruise begins so that changes or problems can be noted as early in the "failure" cycle as possible.

Good luck, you hopefully dodged a bullet. Flush the unit ASAP to get any salt water out that may be there.

Xsbank 03-11-2015 03:01 PM

Hopefully, it's coolant. You've had the catastrophic, now you need expert advice. Definitely flush it but get someone to look at it. Sunchaser is so correct about the coolers.

Why didn't the survey catch it? If it's salt water, it might have sat in there for a long time...

chc 03-11-2015 06:25 PM

Might also get input from Lots of knowledge there as well

windmist 03-11-2015 07:48 PM

Thanks everybody. Looks like it was a flash alarm. I think I mistook foaming oil which I checked right after a 2 hour run, with water being in the oil. And then when I removed the oil using the built in pump, it looked like water was coming out at the end but it must of been just oil.

I poured the used oil into clear containers and let it sit for a couple of hours. I could find no evidence of water in that oil. I also removed the hose from the drain plug and just good oil drained out. Looks like I over reacted. Sorry. By the way, a new heat exchanger from Cummins is just $881 and they have one in Portland. Dodged that bullet.

Good thing is with all your help, I learned a lot. Thanks again.

sunchaser 03-11-2015 08:03 PM

Good deal Windmist. :thumb:

For grins, you may want to check with Seaboard regarding the price of their HXs. I have two new ones on the shelf that I'm probably going to sell soon, but they are smaller than what you need, good for a transmission hooked up to a 250 HP or less engine.

Alaskan Sea-Duction 03-16-2015 04:14 PM

Sunchaser, you are letting him off way too easy! We want a training session on how to properly identify water in oil please! Pictures and everything!!!:blush:

Cheap scotch and cigar would be considered in your sentencing.....:socool:

Glad you found it.....

bayview 03-16-2015 04:29 PM

Whoh! Tranny oil is not usually visibly dirty unless very high hours or something is wrong. Water in oil will not separate once it is mixed well. The color however is baby $hit brown, sort of dark mustard without any burnt smell.
It is not hard to remove the cooler on that engine and pressure test it.

Ski in NC 03-16-2015 04:56 PM

Foamy oil sometimes happens, and it can look dirty or as it is containing water. Just let it sit an hour or so and check again.

If you are under way, drip some on a clean surface and let it settle there. Foam eventually vanishes leaving clean oil.

If your oil is not pure clean yellow, or pure clean atf if that is used, change it. Normal trans does not crap up oil, or not very fast. Some clutch facing material is shed, but that is over lots of hours. Bottom line, if does not look clean, change it. Water in it, likely gear cooler.

The spoon/flame trick is a very good test for water presence.

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