I recently bought a 1995 C36 w/ M-35 engine (30 HP@3200). During the pre-purchase survey, the Hurth 100 transmission was flagged as functioning, but questionable. SInce everything else was good we did a little price adjustment and completed the sale. Now, after a few trips, it is clear that the transmission is toast and rapidly failing. We are tied to the dock until I get this resolved.
Negative posts about the Hurth 100 on this forum and others lead me to believe that I need an upgrade - not just a rebuild. I'd like to find a reliable solution with a minimum of required modifications to engine location, prop shaft, etc. Candidates so far include the ZF 12, ZF15, PRM 90, and the TMC 60. Part of me wants to move away from the ZF/Hurth design, but the PRM 90 and TMC 60 are both longer and will likely require more modifications.
I'm looking for input / insights from anyone who has done a transmission upgrade like this. I'd like to move quickly as we are tied to the dock and summer is slipping away. Thanks for your help.
Steve Bogert / Bonnie Sprague
"Wild Spirit"
1995 Catalina 36 Mk II, Tall Rig, Fin Keel, Hull #1412
Bellingham, WA
Our boat came with a Hurth ZF10 M. I don't know what, if any differences are between that and the Hurth 100. Approaching a thousand hours. No issues (other than a noisey polymer damper plate in the bell housing- noise appears to be due to play in the spline area of the shaft). I'm contemplating bringing it to a shop to have the discs replaced and a general check up this fall...as a preventative maintenance measure.
Paul & Wendy Keyser
"First Light"
Rye NH
2005 C36 MKII #2257
Wing, M35B
My 95 failed last year. I replaced with a ZF10M which is same size physically so no modifications needed. The A ratio is slightly different though. Old gear was 1.79. New is 2.04. So if I am correct, you have to turn higher rpm's to get same forward movement with a fixed blade prop. Correct me if I have that wrong guys. But at the same time I added an adjustable feathering (Variprop) prop so it didn't matter.
If this current ZF gear lasts as long as the first - (20+ years) I'll be happy!
Pat T, 1995 TR, wing keel, #1388
"Liberty Call"
Burnham Harbor, Chicago
The ZF12 has slightly larger measurements. I have the numbers at home. Its about a 1/2" to an 1" on drop and length if I remember correctly. But the price of the ZF12 is much cheaper than the ZF10 which is no longer made except in speacial order batches. Last I checked Catalian Direct had one for about $2750.
Tad Davis
Simpler Times
1989 C-36 MK I #1004
Redondo Beach, Calif.
Anyone contemplating a Hurth overhaul or a PRM90 replacement should feel free to call me at my cellphone 503 358 5102 to discuss. A new PRM90 can be done for about half to a third the cost of overhauling the Hurth. I’m posting off my iPhone, otherwise I’d provide a Lot more detail. So call me. (Steve, I got your email but am running too fast to respond properly .)
Larry Brandt
S/V High Flight #2109
Pacific Northwest, PDX-based
2002 C-36 mkII SR/FK M35B
Thanks for the input everyone (And Larry, thanks for calling). I finally decided to upgrade to a ZF-15M. The deciding factors were: Close match on geometry (only 1/2 inch taller and longer), Close match on gear ratios, and Higher rated capacity. I've only got an hour on the new gear so far, but it seems to be running great - and a lot quieter than my old Hurth.
Again, thanks to everyone for your help.
Steve Bogert / Bonnie Sprague
"Wild Spirit"
1995 Catalina 36 Mk II, Tall Rig, Fin Keel, Hull #1412
Bellingham, WA