New Transmission for 34-2 / M25xp


Member III
Picked up a new Twin Disc MG 340 along with a new damper plate this morning to replace my occasionally slipping Hurth HBW50 and will be attacking this project in the near future.
Have been reading all I can find and the job seems like it should be fairly straight forward (yeah sure!)
Has anyone done this job on a 34-2 ? I would appreciate any advice on the pitfalls that I may expect or what not to do.


Contributing Partner
I have not done that, but I can say that you will have to deal with the different dimensions of this versus the HBW50. When I changed to a ZF10, that was the big challenge. It was slightly longer and slightly taller, both. I see the twin disc dimensions here:

Where did you buy it and how much was it?

Frank Langer

1984 Ericson 30+, Nanaimo, BC
I replaced our Hurth 50 with a twin disc 340MG years ago and it was a perfect fit. It was a different boat and engine, but if the Hurth fit, the Twin Disc should fit too. The only thing that needed changing was the linkage on the wrong side, but that was an easy fix with a small part.


Member III
Thanks for the replies. Not too worried about the dimensions, the height offset is about 4mm and the length is about the same. Plenty of adjustment on the mounts to go up as well as the for shaft to go back. My main concern at the moment is how everything goes together in the bell housing.
Where did you buy it and how much was it?
Purchased everything from Federal Marine Transmissions Inc.
Trans $1139.00
ZF damper $295.00

Mr. Scarlett

Member III
how everything goes together in the bell housing
When I changed my HB50 for a ZF10 it bolted right in. It's a standard bolt pattern if I remember correctly. I was surprised that the unit doesn't bolt on from the outside. Seemed like a cruel engineer joke, since the engine is in the bilge and it meant hoisting the engine out with a modified mainsheet. Of course then you say to yourself "why don't we paint the bilge while we're at it?", then, "before we paint, let's tidy up this wiring", and, "How about this fresh water hose?".
You should be done in 4-6 weeks:D


Sustaining Member
Back in 2018 I replaced my old Hurth with a Twin Disk. I didn’t do the work myself, for a variety of reasons, but I recommend that you also install a “Drivesaver” between the trans and shaft. This was recommended to me by my marina that did the work. Considering the amount of money and time you’re putting into the boat it might be worth it to protect it all. I also had to relocate the heat exchanger so that I was able to access the Twin Disk transmission fluid dip stick. Here’s a link to that story:


Member III
When I changed my HB50 for a ZF10 it bolted right in.
I considered the ZF10 but found that the unit has been discontinued by ZF. Another contender was the Newage PMR 60D until I was told by two different dealers that they were problematic and noisy. That narrowed the field to Twin Disc which in August seemed to be out of stock nationwide.
My yard recommended Jim at Federal Marine Transmissions who turned out to be a wealth of information. I ordered the trans in August with an expected delivery date in mid September that turned into late October. Jim was also able to get me a Sachs damper plate at the old price of $295. Sachs is owned by ZF who just raised the price of the damper to $430!!
Feel lucky to have gotten my hands on the stuff !
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Sustaining Member
Thanks Bolo ! Just dropped the engine back in and encountered the same problem.
Looking into using your fix.
Its an easy fix. I had to go a little over board (no pun intended) with the bracketing because I live 2 hours from the boat so I had to make it a bit more adjustable. It’s a good time to give the insides of your heat exchanger a good cleaning too since it’s going to be off. You’ll most like have to replace hoses going to and from the repositioning of the HX so be prepared for that too.


Member III
Engine back in her nest " Bolo modification" completed !


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Member III
Been at this project since early December with numerous interruptions due to weather and travel. Engine and new trans are back in their home and all plumbing has been re connected. Still need to reconnect wiring and shift cable. I have an Edson pedestal ( push shift handle forward for foreword). Are there any modifications that need to be made as far as the position of the shift lever on rhe MG340. Can I leave it in the 12 o'coock position or do I need to move it to 6 O' clock?


Member III
Purchase the vertical bracket (the first time) from Beta Marine and mount the shift lever at the 3 o'clock position.


Member III
Happy to report that mission is complete and successful. Along with the new trans and damper plate I replaced the old sound dampening insulation in the engine compartment with 1" thick insulation. Engine noise / vibration seems to be about 50 % less with just a bit of lazarette cover rattle over 3000 RPM. (final in water alignment to come). Three hour trip from the yard to my mooring was smooth and uneventful.
Here's a rundown on what I did.
I hung a chain hoist from the forward most point of the companion way and lifted the engine off of the mounts. This allowed me to swing the engine out of the compartment and lower it onto a furniture dolly and block it in place with 2 x 4 blocks.
Using a chain hoist gives you really precise control of the lifting process and I was easily able to get the engine in and out of the compartment by my self.
eng out.jpg
Once the engine was out and turned sideways in the galley the bell housing was easily removed exposing the damper plate on the flywheel.

Old damper compared with new. Zoom in on the old one and you can see the wear on the teeth.
damper old.jpgdamper new.jpg

New transmission bolted to bellhousing.
bell housing.jpg

New sound deadening insulation installed and everything back in it's place.
back in.jpg

All in all this went smoother than I expected. Once the engine was out the bell housing trans, and damper plate came apart and went back together with out a hitch.
The project snowballed a bit for installation of the Bolo modification (see above) and repair of the coolant filler neck overflow tube that I broke off during removal of the engine. A big PITA and a post for another day.
Total cost was just under $2100.
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1990 Ericson 28
All of this work looks great. Well done! I might suggest moving harbors, changing clubs, and finding new employment before I find you to do this work a second time. :)


Member III
Now that's some impressive DIY engine work...and a bit beyond me, I'm afraid
Thanks Christian. Approached this one with much trepidation. The transmission has been on and off wonky since we bought the boat six years ago. Had a lot of time to study and would have been in the dark if not for my predecessors here.