Frothy transmission fluid

[Moonfish]

Discovered my Lehman 120 starboard transmission fluid turned frothy white today during a 3-hour run. My first thought, as there is no sign of leakage on the pan under the tranny, is that the cooler unit has failed and leaked water into the transmission. Looking into replacements I have the option of a copper unit (2c207) or a CuNi/Copper-Nickel unit (2c212CN). Cost is pretty comparable.

Which one is better and why?

Thanks!

 

[twistedtree]

It does sound like water in the oil. I would get it out of the gear as soon as possible and change the oil a couple of times with short operation between runs to get the sea water cleaned out. Of course bypass the failed cooler when doing this.

Also, send out a fluid sample to confirm what's in it.

As I understand it, cu/ni is the more sea water resistant material.

Perhaps consider replacing the coolers on both engines. If one has gone, the other might be close behind.

 

[C lectric]

I vaguely remember something about the Velvet drive holding water in some part of the gearbox and flushing may not clear it out. I can't be sure so phone around and ask a reputable rebuilder. These guys have been mentioned many times here. I have no personal experience. Ask.
https://www.harbormarine.net/transmission-service

I agree about the oil sample to confirm one way or the other about sea water entry. .

Froth can also be due to air entry before the pump. The pump then beats the air into the oil. THe oil sample will tell you which by eliminating or confirming the seawater.

BUt regardless assume seawater entry and get it out fast or rusting may damage parts.

As for replacement gear coolers use the Cu/Ni. Far more seawater resistant. Also look for provision for zinc anode pencils.

 

[jleonard]

I vaguely remember something about the Velvet drive holding water in some part of the gearbox and flushing may not clear it out. I can't be sure so phone around and ask a reputable rebuilder. These guys have been mentioned many times here. I have no personal experience. Ask.
https://www.harbormarine.net/transmission-service

.

The water/oil stays in the reverse cylinder. The tranny has to be turned upside down to drain it. That's what I was told by an old time boat mechanic wo worked on lots of Velvet Drives.
It also might be possible to suck it out via one of the plugged ports.

 

[siestakey]

Ugh keep us updated!! sorry!!!

 

[Ski in NC]

I have been involved in several BW VD's that got water in for one reason or another. All we did was several fluid changes with running the boat in between. Try to blow out cooler on each change as it holds wet oil too. Or run between changes with cooler bypassed, just don't run too long and monitor temp. It is true that milky oil hides in these, thus several changes needed. Just don't let it sit with the wet oil, things rust.

Keep changing fluid til no milkiness noticed. As in NONE.

Those gears lived, several years of good service afterward.

 

[Comodave]

Definitely go with the copper/nickel one.

 

[SoWhat]

Milky fluid would indicate water. Replace all cooler s with CuNi. If one went, the others are next. Failure to replace zincs in heat exchanger is probably the biggest cause of corrosion. Also make sure external surface of coolers and heat exchangers are electrically bonded to engine. (ie, no paint under straps) If the boat is not used for a couple of months drain the raw water system, preferably flush it.

I'm not convinced changing the fluid a couple of times will flush out all the water. The drain is higher then the bottom of the pan so you will always have some contaminated fluid (unless you turn it on it's side) Sucking out fluid with tube won't help because rev. piston is full of fluid and tube can't reach the corners due to baffle. Any water will accelerate corrosion.

PO of my boat left water in the port tran. I had to replace every bearing. Stbd tran just needed clutches and seals.

 

[FlyWright]

When I recently replaced my two oil coolers, I was advised by my Perkins expert to make sure I bought the CuNi unit, so I did. I didn't bother to ask why.

 

[FF]

"I'm not convinced changing the fluid a couple of times will flush out all the water."

Perhaps , one simple method of getting rid of the water is to operate the boat with the tranny oil over 212F- 100C .

A nice long cruise , with a check every hour to see if the oil level dropped might work.

 

[diver dave]

Everyone has water in ALL their oil.
The issue is when the oil is saturated and the water is dropping out of suspension. That relatively pure water then, is pumped around like it was a good lubricant, and it is not. If agitated, it emulsifies, but later will drop out of solution (it could take a long time).

So, heating oil will actually increase its ability to hold water, up to the point it boils out. But most transmissions don't operate above 100C. So, you do want to lightly run the tranny to heat it and mix it up, and then drain and refill. Repeat as needed. I don't think it is necessary to disassemble, ATF is cheap.