Smaller engines were originally equipped with the Hurth HBW50 transmission. Larger engines used the HBW100 transmission. Unfortunately, the smallest transmission has been discontinued entirely. However, this replacement transmission, ZF's 10M with a 2.05:1 reduction ratio, is a bolt-on replacement for both transmissions except it is about 1" longer front to back than the original HBW50. If you are replacing the larger HBW100 transmission, the overall length of this replacement ZF 10M, is the same.

Sadly, this small transmission, the closest replacement to the HBW50, is built in limited quantities which drives its price up. In fact many customers report they are being told this transmission no longer exists. This is not true. We have been receiving 10M transmissions regularly. But apparently ZF doesn't really want to build them because every shipment we receive is substantially more expensive than the last. For a less expensive replacement (that has more differences) consider the 12M transmission offered below under "May we also suggest"

Engines that originally used the HBW50 transmission:
• 5411
• M12
• M2-12
• M-18
• M-320
• M-25
• M-25XP
• M-25XPB

Engines that originally used the HBW100 transmission:
• M-35
• M-35B

Boats that may be able to use this transmission include:
• Capri 26
• Catalina 25
• Catalina 27
• Catalina 28
• Catalina 30
• Catalina 310
• Catalina 34
• Catalina 350
• Catalina 36
There may be others as well, and not all of the above listed boats can use this transmission. Check the model of your engine to be sure.

Critical Dimensions (see "Read More" below for detailed specifications)
• Front to back (L + L3) : 207mm (8.15")
• Output shaft drop from crank: 72mm (2.83")
• Reduction ratio: 2.14:1

Important differences when compared to HBW 50 transmission
• Front to back (L + L3) : +25mm (+0.98")
• Output shaft drop from crank: No change
• Reduction ratio HBW50 vs 10M: 2.05:1 vs. 2.05:1 (same)

Important differences when compared to ZF 12M transmission
• Front to back (L + L3) : -12mm (-0.47")
• Output shaft drop from crank: -10mm (-0.39")
• Reduction ratio 10M vs 12M: 2.05:1 vs. 2.14:1

1) In most cases the extra length of this transmission compared to the original HBW50 will not cause an issue. But in some boats, the Catalina 28 MkII and the Catalina 30 for example, the extra length makes installation more difficult. It is your responsibility to compare all dimensions before ordering to ensure this transmission will be a proper fit to your boat.

2) The transmission has been tested and then drained of oil prior to shipment to avoid being classified as "hazardous material" due to flammable liquid inside. Be sure to add oil before using.

3) These transmissions are shipped from the factory to the West Coast on a pallet. They are then repackaged and boxed individually by the warehouse. Don't expect a fancy printed box. You may find a bit of residual oil in the box that has leaked from the breather tube during shipment.

4) Transmissions do not conform to the shipping table in the Shopping Cart. Additional shipping must be calculated. When you place your order we always call with a shipping quote before billing your card. For a quote in advance, just call 800/959-7245.