With roughly 2500 known hours on my M25XP and original Hurth HBW50 transmission, it has become time to replace the Tranny. I didn't think this would be a big deal because I had purchased a "rebuilt" HBW50 on Craigslist ($300), complete with invoice from Harbor Marine in Everett, WA. Only it probably wasn't rebuilt by them.
As I learned from Mike in the tranny shop--super guy, and very knowledgeable--it is a not uncommon scam to sell one of these representing it as "rebuilt' and with a Harbor Marine invoice showing the rebuild. I live close by and brought in my transmission so he could verify whether it had, in fact, been rebuilt by them. He showed me why (output shaft had some play and no evidence of the sealant they use when putting the transmission case back together) they probably did not do the rebuild.
So the choices come down to (1) rebuild or (2) replace. Very few people recommend rebuilding a 30 year old Hurth HBW50. They don't enjoy a great reputation, and the rebuild cost I was quoted from Mike was roughly $1800 and 30 days out.
As for replacement, it is either stay with an upgraded Hurth (ZF12m) or go to one of the new transmissions with the cone-type clutches. Both are bolt-on replacements. These are either the Newage PRM-60 or the TMC40P. The PRM and TMC are very, very similar but with small dimensional differences. It bears mentioning that Harbor Marine used to sell the Newage PRM60s but no longer does. Ask Mike about that.
Common issues to both:
--you've got to remove the bell housing to unbolt the HBW50 and to install the new Transmission. At a minimum, that means I'm going to lift out the engine into the galley area to do this.
--you've got to replace the damper plate with a new Sachs while its out.
--as long as its out, replace the 32 year motor mounts with new.
Cost/Benefits of the ZF12m:
--gear shift on the same side as the HBW50 (no surgery on the engine bed)
--its more expensive ($2300)
--its bigger dimensionally than the PRM or TMC which means both raising the engine higher and cutting down your prop shaft as the "overhang"--distance from front of prop to cutless bearing/P strut--will increase by 1.5 inches.
--I couldn't find anyone who recommends them over the PRM or TMC alternatives. In a telling post from 2016 or so, Maine Sail basically endorsed running away from the new ZFs and to the TMC40.
--gear ratio is 2.14:1 vs. original 2.05:1 for HBW 50.
Cost benefits of the PRM/TMC:
--less expensive ($1260 for the TMC)
--smaller dimensionally. When installed you have to raise an M25XP 5.5mm due to lower output shaft on the TMC 40, and the "overhang" (distance from prop to strut--usually a shaft diameter (1")-- increases only 4mm).
--shift lever on the port side. This means a little more effort to adjust the shifting cable and/or adjust the cone clutch (which is represented as being "self adjusting" but which may need to happen sometimes). The adjustment of the cone clutch is actually covered in the TMC40 and PRM60 manuals.
--Have to cut away a small area of the port engine bed rail, just aft of the rear port motor mount, to make room for the port side shift lever. (roughly 1" deep and 3" long)
--Have to alter the location of the Heat Exchanger to access the dip stick and fill. As you know, that is already difficult with the HBW50. I have to loosen my 3" Sea Kamp HX to fully extract the dip stick. Noah has a great post on how and where to relocate your heat exchanger for better maintenance access on the tranny, so I am going to do that anyway.
-gear ratio is 2:1 vs. 2.05:1 for HBW 50
Choosing the TMC40:
Based on overwhelming positive reviews vs. the ZF12m, I chose the TMC40P. This was reinforced after I spoke with Joe DeMers at Sound Marine Diesel (CT) who is a Beta dealer and who sells a lot of TMC transmissions as well. Generous with his time over the phone, he went through all the considerations when putting in a replacement transmission for my engine. There is also a Beta Marine document titled "Conversion from ZF5 (Hurth HBW50) to TMC40" which fully explains those considerations.
I ordered my TMC transmission ($1259), 4 new motor mounts at $49/each, and new shift bracket and hardware ($98) from Joe.
(FYI: The motor mounts are dimensionally the same ones that Catalina Direct sells for $180/each!)
By the way, I also went down the road of doing a complete re-power with a Beta 25. I'm pulling the engine anyway to replace the transmission. Problem is that on the left coast there are no Beta 25s in stock. Serious supply chain issues in getting Kubota cores to Beta in England. Earliest "projected" arrival--which is very soft--is March 2023. If you're not on the left coast, they have stock out of North Carolina. I operate as a charter boat so I need better definition than that and don't want to interrupt the season for an engine replacement. But, when the supply increases I can buy a new Beta 25 "bobtail" and attach the TMC40 to it.
Hope this helps anyone having similar issues/thoughts.
Patches
Thanks for the thorough analysis. If you can remember, post a few photos when you have it installed. It would be interesting to see the modifications in situ.
Thx Patches! Great info. I rue the day when my H50 eventually dies....
Patches; Just to clarify: the brand/model you selected is also known as "Twin Disc" — and previously mentioned/used by some other Forum members. Correct?
Yes, TMC = "Twin Disc."
Great write up, thanks. Do you keep or exchange the old HBW50 and m25xp? If repowering, why not upgrade the hp to the Beta 30?
I'm continuing to use my M25XP engine--only changing out the transmission for now. Not much, but some, value in the replaced HBW 50 as a rebuildable core.
My understanding is the Beta 30 uses a different (and larger) Kubota core and would be tighter in my Mark 1 engine compartment. The local Beta dealer came down to the boat and confirmed this.
Just have LogoFreak build you a bigger engine compartment! :abd:
Comment strictly in fun...
Good one Noah!! Logo is definitely making space about his boat. Perhaps we should having him look into the engine bay!!
I heard that :lol:
I can attest to the twin disc, replaced the hbw50 in my m25 I had in my Catalina 30, it's still going strong!
I actually looked into the beta hybrid engine, can't remember which model, likely the smallest one. It meant that you'd have to cut out the rear "shelf" up in order to fit that engine, no thanks!
A better option was to stick a panda dc genset in place of the engine and install an ocean volt leg under the aft bed, however that just doesn't make ANY financial sense and the advantages of having the ocean volt setup aren't quite achieved with our hulls, minimum water speed for getting some regenerative charge is 6kn, I'd prefer having a boat with that setup that could do 7~8 average.
Noah : That's why I went with the M25XPB engine. Even then I had to do some rewickering of the engine mount stringer to get everything to fit and line up!!
Would have loved to install a M35BC engine, but that would have been a rebuild of the interior!!
A few thoughts
For what its worth, I replaced my HBW50 on my M25XPB with a ZF10 back in 2017 myself. I did not pull the engine or need to pull the bell housing to remove the HBW50. I did, however remove the bell housing after pulling the transmission to replace the damper plate. Pulling the tranny was a bit of boat yoga but, not that big of a deal for me. A few bolts after pulling the control cable, coupling etc. and out she came. BTW, while I was at it I replaced everything all the way back. New SS shaft, stuffing box, prop and added a flexible coupling.
Guys : If you want to use to your old shaft with a new ZF10 or Hurth 100; you are going to have to shorten the shaft. I see that Bill installed a new (shorter) SS shaft!!
A thought
Ron, If I recall it was an 1" longer. Do you really think that would make that much of a difference?
Or, replace it with a Twin Disc TMC-40 as I am and it is only 4mm (>3/16") longer and 1/4 of the price of a ZF10 ($1259 vs. $5000 on CD). I'm mid project right now, having removed the exhaust riser and heat exchanger, drained coolant form the motor, and removed the alternator and wiring from the motor.
I'll report back when I've successfully swapped the gearbox and relocated the heat exchanger.
Patches
Rock & Roll!
Quote from: Patches on January 12, 2023, 05:49:43 PM
Or, replace it with a Twin Disc TMC-40 as I am and it is only 4mm (>3/16") longer and 1/4 of the price of a ZF10 ($1259 vs. $5000 on CD). I'm mid project right now, having removed the exhaust riser and heat exchanger, drained coolant form the motor, and removed the alternator and wiring from the motor.
I'll report back when I've successfully swapped the gearbox and relocated the heat exchanger.
Patches
Quote from: Bill Shreeves on January 12, 2023, 01:48:48 PM
Ron, If I recall it was an 1" longer. Do you really think that would make that much of a difference?
Bill,
Yes, because of the clearance required between the prop and the rudder.
As well as (possibly) violating the "rule" that the prop should be no farther than 1in. behind the strut.
Guys : I agree with Noah " rule of thumb - the prop should be one shaft diameter behind the strut".
A thought
Well...change of plans.
The decision to go with a new transmission was based on the assumption that the motor was good to go for another few seasons (at least). I take extremely good care of my motor, and have added much new while its been on my watch. It ran super reliably, didn't smoke, and--until recently--didn't leak any oil. It has approximately 2500 hours since new in 1990. Even so, the new leaking was toward the back of the engine, relatively minor, and the oil level never got to the level where I was adding new oil between changes (roughly every 65-75 hours).
So, I'd purchased a bunch of things in preparation for the tranny swap: new motor mounts, hanger bolts and nuts to secure them, and damper plate. I also fabricated a new mount for the heat exchanger out of 1/4" aluminum angle stock to hang from the underside of the rear berth, and purchased the new hoses to make the extra run from the engine.
We pulled the engine on Wednesday to replace the transmission and placed it on the galley floor. We'd prepared the area with some plywood and drop cloths. After removing the bell housing, we saw some oil on the inside suggesting the need for a new rear seal. No biggie. But my mechanic, a very experienced guy, showed me how there was "end play" in the main shaft which would require a much more significant rebuild to remedy. In his view, putting in a new seal would be--at best-- temporary and the leaking would be back within a matter of time.
So, time to choose. I could do "half a re-power (transmission only and assorted shorter term fixes like the rear real)", get through the upcoming charter season, and decide to re-power a year from now. Or, I could do a "full re-power" and pull the engine only once, start the charter season a little later, and be done with it.
Like many others facing this choice, I thought about rebuilding to get several more years out of the (otherwise) super reliable motor. I LOVE that motor for its ease of maintenance and reliability. But, it is 32 years young now and I'll be keeping the boat for a while as part of the business. I'd already decided that in the event of a re-power it would be a new Beta 25, to the exclusion of the M25 XPB or a 3 cylinder Yanmar.
So, I ordered a new Beta 25 which I'm told will be shipped in "March." I hope so. In the meantime I'll be able to make many of the preparations in the engine bay pending its arrival.
I'll also be selling a couple of the items I recently purchased for the original M25xp, like the Compass Marine 105 amp small frame alternator which I added as part of my electrical upgrade 2 years ago, as well as some spares. So, check the "parts and pieces" classified if you need something for your M25xp. I don't think I'm going to part it out, preferring to sell it as a complete motor with the original alternator.
Patches
My transmission just failed which resulted in a 50 mile tow through Kent and knapps narrows in some rough weather/waves action. How is the project going? Any additional advice or suggestions as I begin the process? Very nice and detailed write up.
Thanks
Paul
Paul : You have a 37 year old engine and (as happened with me ) you could be facing oil seal failure/s. I'd advise that you just get a new engine w/transmission so you can get away from the dock and do some sailing!! I wound up pulling and fixing my old (5000 hrs) engine 2 times and the third time I said - ENOUGH!! I just got tired of playing mechanic rather than being a sailor!!! Treat Yourself !! thumb:
I went with the M25XPB where I could use the same wiring connections, same throttle /gear shifter connections and the same Catalina engine instrument panel.
A few thoughts
Thanks for the advice. Definitely considering that route as well.
Ron -I see you are in the Chesapeake area, where did you get your new one?
Wish I could tell you I am finally finished with my Beta 25 install, but can't--just yet.
The Beta 25 has a manual fuel pump on the engine which--in theory-- is very simple to operate in order to deliver fuel from the tank to the engine, and then to bleed the system. Both my mechanic and dealer said you can take out the old electric fuel pump as it wasn't needed. So I did to create a little more room under the head sink for a new Racor 500fg separator, and moved the new strainer to the back side of the head bulkhead under the shower sump switch. I then cut in a 6" X 6" access door (just below the switch and above the shower seat) that allows me to check the strainer and clean it very easily.
After sorting out the external regulation, electrical and cooling connections, I set about trying to bleed the engine with the "manual" pump on the engine. Wasn't pulling fuel up through the bleed screw on top of the primary fuel filter on the engine. Checked for air entry everywhere. At one point, I thought I had it isolated to between the new Racor and the tank. I pulled the pick-up tube from the tank-- both tube and shut off valve were clear. Pulled the vent tube and vent, both clear.
I then did what I should have done initially. I took a short length of clear hose from the inlet side of the manual fuel pump to a Jerry can with diesel. Operating the "thumb" lever on the fuel pump, I confirmed nothing was getting pulled from the Jerry can: Bad manual fuel pump.
So I'm re-fitting the old electric fuel pump to the system and have a warranty claim on the OEM manual fuel pump. Not what you want with a brand new engine. Hopefully will get it started up today.
I have to say, Joe Demers at Sound Marine Diesel has been terrific to work with. He picks up the phone, and cheerfully answers my many questions about the engine and installation. Another person from Beta carefully walked me through the external regulation set-up on the Iskra 120 Amp alternator.
Again, I'm hoping to do a more comprehensive write-up once I'm done with Sea Trials.
Patches