Replacing Hurth HBW 50 with Twin Disc TMC 40?

rob · August 09, 2015, 09:11:54 AM

Has anyone replaced their Hurth HBW 50 transmission with a Twin Disc TMC 40? The Hurth in my 1989 C34 (Universal 25XP) is on its way out and I've learned they are no longer made and fairly difficult to find even a rebuilt one. Sound Marine Diesel out of Connecticut is recommending I replace the Hurth with the Twin Disc which, apparently, is a perfect fit to replace the Hurth 50. Does anyone have experience with this? and/or with Sound Marine Diesel? thanks!

Ron Hill · August 09, 2015, 01:58:56 PM

Rob : Don't know about the "Twin Disc", but most have replaced their Hurth 50 with a Hurth ZF10.

The ZF10 Fits perfectly and is sturdier than the 50 - like the Hurth 100

A thought

Ken Juul · August 09, 2015, 07:08:29 PM

I have no knowledge of the TMC transmissions. The Hurth has lasted you 26+ years. Why change brands. My boat is a year newer and I don't have any transmission issues. Approaching 3000 hrs on the engine so it has seen it's share of use. Perhaps you need a through cleaning and new fluid. May last a couple more seasons.

Dave DeAre · August 10, 2015, 06:34:38 AM

Rob, I have a good used ZF-10 that I would be willing to sell to a forum member. I just sent you a PM
Dave DeAre

rob · August 12, 2015, 02:35:01 PM

Thanks very much Ron, Ken, and Dave for the input. Dave I'll message you offline regarding the ZF100. It seems like that's the way to go if we can make it fit. (Especially with the new shaft and drippless packing gland).

Ron Hill · August 13, 2015, 10:16:52 AM

rob : So you're not surprised--the ZF10 (Hurth 100) is about an inch longer than the old Hurth 50. You might have to cut your shaft accordingly.

The ZF10 bolts on from the outside of the bell housing. NOT from the inside like the Hurth 50!!

A few thoughts

Ron Hill · August 14, 2015, 08:18:14 AM

rob : As I mentioned above, the ZF10 is about a inch longer than the Hurth 50. That makes the ZF10 a more robust transmission.

You might have to cut some of the drive shaft. You'll need to disconnect the flange (holding the drive shaft) from the transmission. Slide it back and see how the shaft is seated inside that flange. It may be that all you need to do is slide more of the drive shaft into the flange to take care of that extra inch?!

In any case, you want the prop on the shaft to only be about one shaft diameter behind the strut (rule of thumb). In your case 1" -- further behind the strut could cause added wear on the cutless bearing.

A few thoughts

chrisyse · September 28, 2015, 06:48:43 AM

The front seal on my Hurth HBW50 is leaking. Should I and Is it sufficient to just check end play of input and output shafts, before replacing seal and reinstalling the engine/xmsn? Also my near by Beta dealer says that any 1989 HBW50 is a risk due to a marginal design and that I should switch to their TWIN DISC / TECHNODRIVE model TMC 40 P marine transmission. I have no idea how many hours on my XP-25 engine. Boat is a 1989 catalina 34.

chrisyse · November 30, 2015, 06:51:13 AM

Dave,
Is the ZF10 still available? If yes, please provide history.
Thanks,
Chris

Dave DeAre · December 02, 2015, 06:29:56 AM

Chris, Yes, my ZF is still available. I just sent you a PM with history.
Dave

Hawk · June 29, 2016, 06:03:31 PM

I'm looking at these issues and note that Maine Sail has posted on the Catalina 36/375 site on April 2, 2015 that he strongly recommends the more durable Techno-Drive TMC 40 over the ZF 10 (Hurth HBW 100). He talks about the thrust washers not being solid bronze any longer...worth a read. Direct replacement but apparently the trans output shaft is 3mm higher although Maine says not an issue once proper re-alignment is done. I'm still pouring over this myself. Any thoughts appreciated.

Hawk

Stu Jackson · July 01, 2016, 04:39:27 PM

Quote from: Hawk on June 29, 2016, 06:03:31 PM
.......and note that Maine Sail has posted on the Catalina 36/375 site on April 2, 2015 that he strongly recommends the more durable Techno-Drive TMC 40 over the ZF 10 (Hurth HBW 100).

Tom,

Would that be reply #8, here?

https://www.catalina36.org/forum/technical-discussion/transmission-slippage

If you've found good material elsewhere on the web, I find it very helpful to provide links. Thanks for the head's up.

Hawk · July 07, 2016, 05:32:02 PM

That's the one Stu. Link reminder noted.
I'm sailing in the Gulf Islands rather than north up the coast because of the tranny but flukes into meeting what appears to be a good mechanic pens the shipyard in Silva Bay, showed me one he's rebuilding. So I'm leaving the boat tomorrow and he will pull it and rebuild it, barring any bigger issue than clutches and thrust washers. All in $500 for rebuild including parts plus $750 to get it off and on. By comparison Foley Engines quoted US$2100 plus shipping and then CDN taxes which with exchange rates puts it at $3000 just for a new ZF 10. Which of course Mainsail says are now to be avoided. AND then got to get it off and on.
I know some guys would try doing it themselves but I'm better off working than spending 3 days or who knows.....
In Vancouver a rebuild kit alone is almost a grand.
So we're going to help keep the island economy running and hope it works.
Will keep you posted.
Hawk

Hawk · July 07, 2016, 06:08:58 PM

I know it's off topic from below but Stu or Ron thinking to get them to fabricate a new ss exhaust elbow since they're working on the engine. Just preventative. Any thoughts?
Thanks

Stu Jackson · July 07, 2016, 09:05:47 PM

Quote from: Hawk on July 07, 2016, 06:08:58 PM
I know it's off topic from below but Stu or Ron thinking to get them to fabricate a new ss exhaust elbow since they're working on the engine. Just preventative. Any thoughts?
Thanks

Tom, I completed a Tech Note recently about replacing a muffler which also included a new riser I bought from Catalina Direct. It's pricey, but I saved $$$ by obtaining a replacement muffler from a really nice fellow boater on sailboatowners.com.

The link is:

http://www.c34.org/mainsheet/html/2016/Muffler%20&%20Exhaust%20Riser%20Replacement.html