Universal 5424 with Hurth Transmission problem

[Obi Wan]

I have a Universal Atomic 5424 (1982 34' O'Day) with a Hurth transmission. The forward gear has started to slip when engaged. Especially when relatively cold. Sometimes need to sit there in idle with it engaged for several minutes before it really starts turning the prop. I don't use the motor that much - mostly to come into or out of our little bayou. I understand it is probably a clutch issue. Talked to a mechanic and he said (without looking at it yet) probably start at $1000 to rebuild the clutch and $3000 to replace the tranny.

My questions:
1. Is this something I can reasonably do myself? I'm an aircraft mechanic, so no stranger to a wrench, but definitely haven't worked on transmissions.

2. Where is the model number of the transmission? I am attaching a picture. Is that it above the gearbox? When I took it, I thought the transmission was just the smaller gearbox housing but now I see it looks like it has a bell-housing similar to a car transmission, which of course makes the removal more difficult than I initially thought.

3. Is there a better bolt-on replacement than the Hurth? I understand from doing a little Googling that they are not that reliable.

Thanks for any advice.

[Cheechako]

Seems like there was a plate on top of my Hurth's... not sure. I had them in 44 and 47 foot boats with no issues whatsoever. They are small and light unlike a Velvet Drive etc. But people have noted issues here on the forum over the years. Mine were old (80's), seems like the ones noted for problems were newer (ZF) but not really sure. The transmission is just the smaller housing behind the bell housing.

https://www.youtube.com/watch?v=8Pdfm0pMH18

There are other threads on CF about removal, google it.

[Sailmonkey]

The modern equivalent of that if the ZF10M, and a plug in replacement is the twin disc/technodrive mg340/TMC 40.

I'd lean heavily towards total replacement, parts can easily exceed the price of the new gearbox. There is no need for you to pay to have this replaced, it's a simple bolt job. The bell housing may need to be removed to disconnect the gear though.

[Obi Wan]

Originally Posted by Sailmonkey

The modern equivalent of that if the ZF10M, and a plug in replacement is the twin disc/technodrive mg340/TMC 40.

I'd lean heavily towards total replacement, parts can easily exceed the price of the new gearbox. There is no need for you to pay to have this replaced, it's a simple bolt job. The bell housing may need to be removed to disconnect the gear though.

So you're saying either a new ZF-10M OR an mg340/TMC 40?

Is the clutch in the gear box or the bell housing?

[Cheechako]

Might want to read some of these first. http://www.cruisersforum.com/forums/...ures-8248.html

[tkeithlu]

Without questioning any of the good advice above, I offer a rule of thumb about tackling unfamiliar machinery - if I can get an exploded diagram of the parts that makes sense, and parts are available, OK, I'm game. If I can't, it's too big a risk. I just did a clutch on an unfamiliar motorcycle on that basis - came out OK.

Second consideration - if they're common, but unreliable, can you exchange yours for a rebuilt? That's a cheaper way of letting the pros do the work.

[Obi Wan]

Based on the above I've already made that decision...will buy a new replacement or rebuilt and bolt it on. But would still like to gather as much info on options.

[topmast]

The bell housing has to come off to check or replace the drive plate but the tranny should unbolt and pull the pilot shaft out of plate(unless it's spline is rusted snug .Then it gets more complicated.Replace is probably good idea.and drive plate should be looked at. (work boats sometimes replace every season)

[Obi Wan]

Workboats sometimes replace the drive plate or gear box every season?

[Jim Cate]

What engine is it coupled to? If it is near to running at its max ratings, an upgrade to the ZF-12 might be in order. I believe that it is a drop in replacement to the ZF10, and has a bit higher capacity.

Once you do the replacement, change the ATF fluid frequently... like every time you change the engine oil. There is only 375 mL in the ZF10 and it can degrade rapidly.

Jim

[Obi Wan]

A Universal Atomic 5424 (24 hp).

Does anyone know for sure if the ZF-12 would work instead of a ZF-10?

[Jim Cate]

At 24 hp, you are well within the specs for a ZF10. Mine is coupled to a 43 hp Kubota, and has lasted for nearly 4000 hours since I replaced it's abused predecessor. I change the ATF (Dexron III grade only) every 150-200 hours.

Jim

[Obi Wan]

I saw this on a marine diesel store site (Sound Marine Diesel) selling TECHNODRIVE Twin Disc TMC 40 P:

"Unlike Hurth / ZF transmissions that use multi disc clutches, this Technodrive gear uses a simple cone clutch. This makes them VERY reliable, robust, and trouble free."

Does that ring true? They are certainly less expensive than the ZF. If they are less expensive AND more reliable, that's a no-brainer.

[Sailmonkey]

Originally Posted by Obi Wan

So you're saying either a new ZF-10M OR an mg340/TMC 40?



Is the clutch in the gear box or the bell housing?

The clutch is in the gearbox, the damper plate is in the bell housing. Some bellhousings require you to remove them to access the bolts holding the gear to the bell housing.

I replaced a zf10m with a twin disc and have been quite happy with it. While I was in there I did the damper plate as well. Not a lot of cash, and a pain if it fails after you've changed the gear.

If you price new vs rebuilt on the gear, I've got a hunch you'll go with new.

[topmast]

Obi Wan ,I was refering to the plate. Down time is so expensive compared to the plate maintenance.If the box is bolted on from inside of bell housing you know where you have to start .