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[kable]

Lost my transmission (smelled smoke) at the start of my last week long vacation, raised the sails, cut the engine and returned back home in rough seas for about 2hrs.  Started the engine at the harbor entrance to motor the last bit to my slip, couldn't get her into gear.  Transmission was already hot/smoked and I left it in forward for the rough sail.  Had to sail into my slip (yikes).  Added oil and seems to work but I don't trust it now.  I want to replace it and other things while I am at it.

Based on all my googling of c34.org and the wider interwebs....

ZF10 vs ZF12
- Price - ZF10 is double the price ($2.5k vs $5k)
- Ratio - ZF12 is slightly different, will it matter? 2.14:1 vs 2.05:1
- Either way I have to push or cut the shaft to 1"-1.5" (separate forum thread)
- Output shaft drop - Have to raise the engine slightly on the ZF12

PRM 60D
- 1/4 of the price
- Ratio is the same
- Same issues w/ shortening the shaft and height
- Have to deal w/ the shifter being on the port and reversed at the helm
- I have heard mention of a 'noise/squeal' but really haven't found a lot of supporting information that didn't end up being contributed to other factors
- BUT I see a lot of positive references to Harbor Marine in Everett and they told me they quit carrying PRM because of quality issues

Techno-Drive TMC-40 (aka Twin-Disc MG-340)
- Recommended by Maine Sail - https://www.catalina36.org/comment/57268#comment-57268
- Price about $1.2k (1/2)
- Ratio - 2:1 - no change
- Shifter on port side
- Seeing multiple references to "trimming stringers"??
- Not clear on shaft modifications, but seems like it needs to be shortened

Anything to consider w/ regards to future proofing "re-powering" etc

Thoughts?

[Noah]

I believe another option may be Twin Disc. Search our site. Caveat: I am not a mechanic.

[Bill Shreeves]

I replaced my Hurth with a ZF10 about 6 years ago.  Because the price has gone sky high for a direct replacement, I'd seriously look into having it re-built.  I didn't rebuild then because, at the time, the cost to rebuild was about 75% the cost to ZF 10.  Not the case today...

[kable]

I updated my post to include my summary of my quick searches on Techno-Drive TMC-40.

I do like the cheaper price and some say better design but the shifter modification and the possible stringer scares me.
Seems like there is both positive and negative comments out there.

[KWKloeber]

One of our c30-ers replaced his Hurth w/ the PRM Newage 60D2 and is happy with it.  The switch wasn't a big deal and I believe that the supplier provided the new bracket ready to bold on.  If it was not his, then a different vendor provided the bracket for a different C30 owner who switched his tranny.

I PM'd you his email, if you want to contact him for more info.

-ken

[kh3412]

Did the twin disk install on my boat.
Yes I had to trim the port stringer but was not a big deal.
You cod do the install without trimming if your comfortable with your shifter being reversed I believe.
If you are interested reach out to me and we can talk.

[Jim Fitch]

Kable - I ended up going with the PRM90 back in 2018.  That's what the transmission guy up my way recommended and the price was great.  He had great things to say about their design and quality and it has performed well but, I have never liked the way it sounds.  I wouldn't call it a squeal, I call it a whine.  It's a totally different sound than the old Hurth.  I'm not even sure if it's louder but I find the higher pitch annoying.  The transmission guy said he'd never heard of that but it did it on day one and it's still doing it now.  I'm not going to pull it out and replace it because of the sound but I'd pay more next time to get the ZF.

As far as hooking up the shift, mine isn't reversed on the helm.  I may have flipped the shift lever on the transmission down instead of up to get the right action but I don't really remember.  I did have to make my own mounting plate for the cable but that was easy.

BTW, hooking my old crusty flange onto the shiny new one on the transmission prompted me to finally get a new stainless shaft, replace the shaft log hose and clamps, replace and all the stuffing, get the prop balanced, have the new shaft flange faced by the pros and replace all the engine mounts.  Everything was all original so this was all overdue anyhow.  My boat is a 1990.

Jim

[kable]

Thanks for all the replies.  I ended up settling on the ZF12m just because of the majority of information on the net and a local sales rep to talk/work with.

Purchased:
- ZF12M transmission from Harbor Marine in Everett, WA
   - Important differences when compared to HBW 50 transmission
      -  Front to back (L + L3) : +37mm (+1.46")
      -  Output shaft drop from crank: +10mm (.39")
      -  Reduction ratio 12M vs HBW 50: 2.14:1 vs. 2.05:1
- Damper plate - 1866-050-002 (hope it fits)
- Vetus K-75 motor mounts
- Federal flexible coupler
- Exhaust Heat Riser and extra gaskets - TODO
- Hot water tank hoses 5/8" metal re-enforced

Process (boat is in the water):
- Days/week before, use pb blaster in a cup w/ q-tips to apply to existing bolts (especially the exhaust riser.
- Pretty much follow this post: https://c34.org/bbs/index.php/topic,293.msg941.html#msg941
- Drain coolant (prep for removing exhaust riser, replacing hoses)
- Lift the engine/trans and move forward into the companion way
- Make a template/marks for where the current motor mounts are located
- Replace motor mounts adding 10mm shim (yellow passivated steel) to raise the engine (required for new trans) (oak or metal?)
- Replace hot water tank hoses
- Remove existing hard coupler
- Replace transmission
- Install old hard coupler (to use for alignment)
- Paint engine
- Replace remaining hard to get to engine wall insulation
- Spray Boeshield T9 on transmission
- Measure and mark the shaft for the position it needs to be moved back to (transmission is 1.5" longer):  Will be removing the old hard coupler and drive saver and replacing w/ the smaller federal flex coupler.  So will need to probably move back 1/2" (TBD).
- Install new Clamp-Collar on the drive shaft (so it doesn't fall out)
- Remove the setscrews in the PSS so the drive shaft can be pushed backwards (someone could hold the bellows to help reduce water ingress)
- Push back (temporary) insert a couple existing set screws/re-adjust Clamp-Collar
- Install engine/transmission
- Install new exhaust riser and new hump hose (TBD)
- Adjust shaft into old hard coupler and re-use keyway, setscrew holes (use old PSS set screws/re-adjust Clamp-Collar)
- Align engine
- Replace old hard coupler w/ new flex coupler, using existing keyway and setscrew holes (this may or may not work???) - mitigation: continue to use old hard coupler for couple years until boat is pulled
- Install new PSS set screws w/ drive shaft in its final position

Year or two later:
- Pull boat (standard bottom paint etc)
- Measure distance from prop to strut, how much do I need to cut to get this down to 1"
- Press out cutlass bearing
- Pull prop and shaft
- Send off to be cut, re-key way and fit to new federal flex coupler (research pitch on prop because of transmission ratio?)
- Re-install shaft, new PSS set screws, re-align engine in water

Will update with how it actually goes down

[Ron Hill]

Kable : I decided to protect the water heater hoses from any possible chards of fiberglass on the hull under the floor.  So I slid the tubular pipe insulation on both the hoses from the galley side to protect them.

A thought

[waughoo]

Looks like a solid todo list there.  I don't think you need to go with the exact same metal for the motor mount shims.  Some stainless shims might be just fine and likely easier to come by.

[kable]

Update: Removal of engine and transmission

Not a lot of comments to share, it went really well.  No 'problems' to solve.  All bolts cooperated.  My brother-in-law started about 1:30 and by 6:30 we were cleaned up and heading for dinner.

Now I am cleaning, installing insulation, hoses, HX boiled/tested, alternator tested, re-doing the wire harness (yes this should have been done long ago), etc.

I have all the parts and hopefully we can start re-installing later this week.

Thinking about a new alternator, since we need to re-route the circuit anyway.  Any thoughts on a 105 amp replacement?

What about torque specs for things?
- Federal flex coupler
- Bell housing
- Engine mount bolts
- ???

[waughoo]

This is so tempting to me... I would love to remove mine to clean and reinsulate the engine compartment as well as clean and paint the engine.  Looks like good progress.  Keep us updated with photos.

[Ron Hill]

Kable : Read up on Hi-Output alternators in WiKi and numerous posts.  Just make sure you pair it up with an external Voltage regulator.  That way you can dumb down an alternator to about 85 amps. 

Many articles, posts and recommendations especially from Mainsail!!   

A few thoughts

[Ron Hill]

Kable : Look at the pictures and see the amount of oil that was under the right front engine mount (look like the originals!!). That mount is probably shot!!

Do yourself a favor and get some Vetus K75 new mounts!!

A thought