Do all Hurth Transmissions Suck? Need Advice on a New Trans for a MD40 Universal

[mmgrantphd]

Just finished a total restoration of a 1964 Pearson Alberg 35. The entire propulsion system had been removed by a previous owner and I have repowered with a Universal MD40 take out purchased from Sound Marine Diesel. After MUCH work the engine hummed along well until, on the first trial in the bay, the engine suddenly stopped...clunk. Found out the transmission (a Hurth HBW 100 or ZF 10M whichever label you prefer, they refer to the very same transmission) was screwed. After reading, I see that lots of people have trouble with Hurths and many of the vendors who sell them.

I need a reliable transmission for the Universal MD40 and am happy to provide oil cooling, damper plate, flex coupling, great synthetic oil, etc. to ensure it works well. Is there any way I can avoid a Hurth? What other transmissions can I use for this old MD40 (it is a 1984 model)?

Thanks!

Michael

mmgrant0958@gmail.com

[MARINE ENGINNER]

dear mmgrantphd
sorry to hear about your trouble but fror my experience with ZF untill now they are quite reliable if you change the oil evey 6 months or every 500hours the oil is the common ATF DX III . The problems i have seen are only that they start to slip after running more then 5000 hours on charter yachts and with a fiber discs repair kit you are again sailing.

your tranny was used ? did you detect what was the problem?.is the damper plate aligned ? misalignment of engine-damper plate-tranny results on tranny problems.

About changing the ZF10M don't purchase any kanzaki model (yanmar transmissions) they use a cone clutch. they are very "sensitive" in everything handling and money


M.E

[tdoster]

I truly empathize with your position and frustration but, I don't agree they suck as a rule. They are good gear boxes when treated well and most of the issues were from neglect or incorrect sizing of the engine/box/prop as well as shifting too slowly into gear. Not to mention fluid changes that many people neglect. This one lasted 30 years in a salty bilge before it failed with the 2nd owner.

If you buy a new one, chances are high it will outlast your MD40 and you wont have to modify anything to bolt it on. I think the math works in favor of that.

[sailr69]

you can install a water cooler which greatly prolongs any repairs needed. change oil every 100 hours and do not sail with the gear in forward, put in neutral or reverse

[mmgrantphd]

Thanks to you three who have posted replies. I took the transmission apart and the problem was a blown tapered bearing (see pics). It is probably simply due to age of the transmission. I talked with Mack Boring in New Jersey and have ordered a new Hurth HBW 100, new damper plate, new flex coupling, and new water cooler. Also asked for a hose barb fitting for oil drain so I can lead a hose from it, permanently attached, down to a place where draining the oil will be much simpler. That will make it easy for me to drain and change trans oil appropriately. Interestingly, the guy at Mack Boring said not to use synthetic oils as they are "too slippery" and cause problems in transmissions (at least Hurths). He suggested Dextran III and I will follow that recommendation. Out with the old tranny and in with the new!

Michael

[MARINE ENGINNER]

mmgrantphd hi
keep your old one for spare parts especially the shafts are very expensive.

the guy in mack boring is correct and you will find it also as ATF DX III and the transmission also has a label on it that recommends ATF oil
remember for the new one change the oil after 20 hours of operation and then every 6 months or ervey 500hours whatever comes first

good luck with your new tranny, hope this will be your last problem


M.E

[Stu Jackson]

Sorry to hear about that. Many skippers do not know what position to leave the transmission in when sailing, and Yanmar engine transmissions are different than Hurths. We have a Hurth, 2800 engine hours. It takes either Ford ATF or Dexron (whatever # they're up to now, like the Super Bowl!). Never mix the two. Change it regularly. Yanmar transmission take regular 30W engine oil. Never do this to a Hurth.

The Right Transmission Gear for Sailing - C34

How to Check the Transmission Oil - C34

Transmission Fluid 101 - link to the message board: Transmission Fluid 101

For some bizarre reason, Catalina 36 skippers have experienced singificant issues with the Hurths in their boats. While our boats are almost identical, and were built in the same factory, side by side, our C34 skippers have NOT had those problems.

[a64pilot]

Careful, some Yanmar transmissions use Dexron, and apparently not all have cones either. Perhaps the ones that have cones use engine oil and the ones that have clutch packs use Transmission fluid?

[Jim Cate]

FWIW,
We were advised to change the lube (Dexron III) in our ZF10 every time we change the engine oil (200 hours). It only holds 375 mL, so it is not expensive. We've put about 3100 hours on it now, and so far, so good. Fingers crossed!

Jim

[forsailbyowner]

In my opinion yes they suck.

ZF/Hurth Marine Transmissions: A Six Step Program | Foley Engines

I would look into a velvet drive. They are nearly bulletproof and cost less than a hurth to buy, fix or rebuild. I bought a sailboat with a frozen trans,(hurth) and in no way would put one back in after reading page after page of search results about hurth failures. Google velvet drive and you will find no such thing. Parts are out of this world expensive. Inflated to point of making you gag. Ive personally seen dozens of failed hurth transmissions. Ive seen them corroded to dust while iron parts around them looked unphased.