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Tech Tip #105: Hurth and ZF/Hurth Marine Transmissions: Old Wine in New Bottles?

Helpful guide on identifying your Hurth and ZF/Hurth Marine Transmission

Most of our Tech Tips about Hurth mechanical marine transmissions have been about maintenance. See for example

and others on our web site. This one is different. It discusses how you can tell if you have a Hurth Company in Munich, Germany or a later model Hurth marine gear manufactured by ZF in Italy after ZF purchased the assets of the original Hurth Company.

Roughly 15 years ago, the Carl Hurth Company of Munich, Germany was purchased by the much larger ZF company, a world wide conglomerate. ZF continued to build the Hurth marine transmission but moved production to Italy. Once ZF Marine took over they instituted a major change in the Hurth marine gear model numbering system and implemented several subtle design changes. People frequently call us after seeing a used Hurth marine gear for sale at a their local boat yard. They often ask for help in unscrambling the model numbers as well as asking if the Hurth mechanical gear they are looking is an original Carl Hurth marine transmission or a Hurth gear manufactured by ZF. Here is how to tell.

Hurth Gear Model Numbers Made Easy

Old Hurth Marine Gear Model Number New Style Hurth Number Current ZF Model Number
None HBW50 ZF5
None None ZF6
HBW5 HBW100 ZF10
None HBW125 ZF12
HBW10 HBW150 ZF15
HBW150V ZF15V1
HBW250 ZF25

Output Flange Change Change

In addition to changing model numbers, ZF/Hurth also changed several design features. The output flange at the rear of the transmission was strengthened. The original Carl Hurth marine transmission had a flange with four ears. The late style ZF/Hurth flange has two ears. The flanges are identical in bolt hole spacing and essential function but the later flange is stronger and preferable on the ZF/Hurth marine gear. We have not seen the same number of broken flanges on the late style flange as we have with the earlier one.

Shift Handle Change

Getting your shift linkage set up correctly is critical. Having good linkage alignment is very important. Shift linkage alignment is so important that it is the second thing , after checking the fluid level, that you should check in your Hurth if you are having any problems. We touched on it in Tech Tip #101, Hurth Marine Gear Shift Position: A Warning. ZF changed the shift handle design when they bought the company to a more rigid, stronger design. Both handles, the early Hurth as well as the late ZF design, slide on the shifting shaft and are interchangeable. The late style ZF designed handle is rectangular in shape, appears to have a brass colored finish, is held on with a better fastening system and appears to offer more attachment points for the linkage. This late style ZF/Hurth designed shift lever appears to have a brass finish because of the protective coating the ZF Factory now uses to add longevity to the former problematic part. We recommend that you use the late style shift handle. The early style Hurth shift lever is just casted “white metal” and will not hold up to the elements. We stock them for retrofitting to an older Hurth and could ship you one today.

This Tech Tip seeks to assist Hurth marine gear owners by unscrambling a confusing numbering system as well as outlining how they can tell if they have an early or a late Hurth gear.