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A bit late on replacing the oil cooler

diver_dave

diver_dave

Advanced Contributor
"Yep; found myself 1/2 thru a

"Yep; found myself 1/2 thru a short Bahamas trip with a leaky U cooler. Sending transmission fluid where it did not belong and in return, depositing sea water in my 72C transmission. Fluids all looked perfect the day before. Now, i've got propshaft rotation in neutral, indicating a shot clutch pack. Anyway, word for the wise, the U coolers may not make 12 years."
 
"That's a bummer....how ma

"That's a bummer....how many times have you given it the acid bath? I've got one that's original and the others about 6-7 years younger..yes, I'm knocking on the desk as I type.

You gonna fix it over there or come home first?"
 
"I went ahead and ran the tran

"I went ahead and ran the transmission a half hour after I noted the issue. It took a quart of ATF, to the horrible strawberry milkshake mix !@#$$%. Not the best thing for it, but then, neither is shooting my inlet at 4 am on one engine! I'll do a test with high load on the suspect transmission to see if it slips with fresh fluid. I know the forward clutch disks are a mess, but am hoping to put off a rebuild for a couple of months. I've got a busy boating month coming up, and a yank and rebuild is not in the plan, just yet.

Oh, and no acid bath on this one at all. But, i've not used zincs for the last several years, but have done a fresh water flush after every use. It's a balance of zinc erosion vs corrosion, I suppose. "
 
"So, what made you pass on the

"So, what made you pass on the zincs - the eroding pencil parts restricting the water flow?

So did you bypass the cooler or just keep adding fluid?"
 
"yes, the zinc clogs the tubes

"yes, the zinc clogs the tubes. I'm going to keep the zinc in the new cooler, but likely not replace it.
The issue started at about 1am on a long fishing trip. Slipping. The dipstick showed a quart low in milkshake. The smart move would have been bypass the cooler for the rest of the nite, I only added fluid. It appeared that when running, ATF exited the exhaust. At shutdown, the cooler drained the seawater into the 72C. I note that the raw water connections are both on the top of the cooler, so any internal leak will be bad news to either the engine or the transmission. I suppose a better design would gravity drain the cooler thru the HE at shutdown.
Or, even better, just replace the coolers at 10 year intervals. At almost $300 a side, they didn't quite make the PM cut."
 
"My buddy has an old blackfin

"My buddy has an old blackfin 25 - single screw. Similar situation...slipping when starting to run home on a saturday afternoon 40 nm offshore. His setup had the merc style coolers, in the raw water line, on either side of the oil pan. Turns out the cooler location doesn't really matter. He's confident to pressure on the inlet side (oil) exceeds the water pressure so any void will cause oil to enter the cooling water stream. He also said the water pressure exceeds the outlet (oil) so the water's going to go back as a substitute for the "cooled oil". (I think the last bit going back in at shutdown won't make much difference during a failure event.)

Ironically, he said the same thing about bypassing the cooler - and he did hydraulic transmissions for ~ 15 years."
 
"I had a similar situation abo

"I had a similar situation about 2 years ago. I was out all day fishing and noted that my port engine was hard to get in and out of gear.

I forgot about it until the next day. I found the same thing, strawberry milkshake. Being Sat AM of Memorial day weekend, I scrambled to locate another cooler and was lucky to find one. That along with a new oil change pump (my other one was home 2 hours away)and a case of cheap tranny fluid I was able to flush the tranny 4 times and somehow saved the tranny.

The oil cooler I got wasn't an exact match, but I was able to rig it up and used it for the year. Last spring I replaced both of them with the OEM part.

I still have the other cooler if someone is looking for a deal on one. It's not a U-Cooler, but has 2 side by side cooling passages. One for the tranny, the other for the engine. I believe it fits either a 1.25 or 1.5" hose. If anyone is interested I can get more information."
 
"Sorry to hear of your trouble

"Sorry to hear of your troubles, diver dave. It points to an important maintainence issue and a potiential time bomb. Those coolers are a blind item with no way of knowing what kind of condition they are in or when they will let go. External appearence probably doesn't tell you very much. Mine could be ten years old or twenty--again, no way of knowing if you are the second or third owner. At around $330.00 each they don't get replaced until they fail and take out a gear or worse, an engine.

I know they can be cleaned and pressure tested. Is there anything else that can be done to assess their condition before disaster strikes?"
 
"Boy, am I glad I run in fresh

"Boy, am I glad I run in fresh water! Seriously. I have great sympathy for those of you that don't.

Jeff"
 
"Jeff; You mean that your sta

"Jeff; You mean that your stainless selflocking nuts on the shaft log don't crevice crack in half? Or, your shaft couplers don't turn to a rust ball in 5 years? Or, your starters don't rust away just because, even dry, they are below sea level? Or, good quality silicon bronze wood screws in the cabin turn to green dust in 10 years? I could go on and on...."
 
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