Hello,
My boat has a ZF/Hurth v-drive transmission with a transmission cooler attached. During recent checking of the transmission fluid level, I discovered what I believed to be water inside the transmission. Today with some help, we removed the cooler discovered a hole in it, and corresponding soft spot in the transmission casing adjacent to the hole in the cooler. This is how the water was getting into the transmission. I believe the hole was caused by electrolysis between the cooler and the transmission case.
So, I am wondering how many other Nonsuch’s with the ZF/Hurth v-drive have a transmission cooler installed?
And for those that do, have you experienced a similar problem?
Thanks Paul and Bob for the replies. Based on the volume of answers, I am guessing I’m the only one with a cooling unit mounted on the transmission. According to my reading of the ZF manual, this optional cooling unit is not necessary for a 31 hp engine like mine. So it will not be replaced. My mechanic is coming on Friday to see if there’s a way to repair the transmission case, hopefully without pulling the transmission out.
Don
CAKEWALKIII
(Peter Grabow CAKE WALK III 30U #430 SHYH - Stamford, CT)
5
Hi Don,
I have the same setup on my 30U with W27A engine and have not (yet) experienced the issue you are having with water entering the transmission from the cooler.
Please keep us informed on how you get this resolved.
In case of interest, I think there’s a pointer to a source of stainless steel transmission coolers in the 2016 discussion thread that Discourse pointed out as potentially relevant to this one: Transmission Cooler Failure - #8 by system
Look for the post about an outfit called Foley. Don’t know if the info’s still up to date, though.
– Bob
Ward.Woodruff
(Ward Woodruff N33 #8 Margery Niantic Bay, CT)
7
Here is the Hurth table regarding requirement for transmission cooler.
For the HBW-150V I read it as max 25 HP (shift lever in A position in forward) continuous power input is the point that you need a cooler.
I do not have a cooler with that transmission and a Beta 35 (35 rated HP). I don’t run at engine rated RPM/HP. I should look up the engine output at 2200 RPM which is where I cruise.
My mechanic was at the boat today to inspect and decide how to fix. Cleaned the compromised area of the transmission casing, the hole is big enough to put my little finger through. He decided to make a aluminum plate, with gasket, to cover the hole. The plate will be held in place with the bolts that secured the faulty cooling unit. He’s coming back next week to flush transmission and install new cover plate.
The cooling unit on my transmission was made of cast iron type steel, attached to aluminum transmission case, not good with salt water or electrolysis. I’m not sure, but I don’t think it was a OEM part. Internet search shows several brass/aluminum/stainless alternatives. Read your manual first, but I don’t think a transmission cooler is necessary.
Don, Thanks for the update and photo. It cleaned up nicely, your mechanic is a keeper. Soave does not have a transmission cooler, one less potential site for corrosion to worry about.
Hearing about corrosion sites others are finding, renews my resolve to keep up with Soave’s preventative maintenance.
Boats with transmission coolers, benefit from periodic inspection and renewal of the isolation layer between dissimilar metals including threads of the bolts. If the cooler is unnecessary, it may be easier to simply remove it.
After struggling with many corroded bolts and screws on Soave, I’m realizing why older boats are not quite as cost effective as I used to think. I am pleased with Soave even though PM is more that I anticipated. Owners with patience, time, and a little money who keep up with the PM are a good match for an older boat.
Looking at the table above I see that my M40 engine with a HBW150 V needs a cooler. Looks like another task for the spring commissioning list. Thanks for bringing this up.
Any idea what (if anything) is recommended between the cooler and the transmission? Dielectric grease seems like a good idea.
Here is photo of the final repair with the new plate installed over the hole. After which mechanic flushed the transmission 3 times to remove any remnants of salt water in the ATF lubricate.
Blake, I wouldn’t be in any rush to add a cooler to your transmission, given the problem mine caused me. Check you transmission manuals and see what they recommend. If your boat has gone this long without one, why would it need one now?
Blake,
I use Forespar MareLube TEF45 to isolate dissimilar metals when a hard layer ( polycarbonate ) is not possible.
A 4oz tub costs about $35 and lasts a very long time. I think there might be an efficient way to get a case of the little tubes, because the staff at the yard always seem to have a handful and leave behind half full tubes. The cost is probably passed thru in the line item miscellaneous materials.
There are many dielectric grease products, the ones that contain teflon seem to be preferred in marine environments.
Don and I concluded that one of the problems in his cooler installation was that it was the lowest point in the raw water side of the cooling system and was always full of salt water with no zinc anode near. It seems likely that any metal block style cooler (rather than a heat exchanger style) would have the same issue. A noble idea to keep the cooling water separate from the oil,… if it doesn’t fail as this did.
