[C320-list] Hurth Transmission Advice

[Warren Updike]

As much as I’ve abused foleyengines.com about their bedside manner or lack
thereof, I do suspect they are a qualified and creditable source for parts,
repairs, replacements and advice for Perkins and ZF/Hurth gears.  Their
latest marketing e-mail makes two good points:

 

O Run a Good Synthetic Fluid. To give your ZF/Hurth a fighting chance, run a
high quality synthetic ATF. Both Red Line and Mobil1 are good choices. Or,
go all the way and run our superior Foley Hurth Hytork fluid. Good synthetic
runs cooler, lasts longer, and is more forgiving of extended oil change
intervals. Spending a little bit of money on a quality fluid is a no
brainer. See Tech Tip # 39, Hurth Marine Transmissions, The Ins and Outs of
Basic Service
<http://r20.rs6.net/tn.jsp?llr=hilr9edab&et=1105015206677&s=6302&e=001RHZTgo
KW00nbHsJLLlPVjlNdE9v9HeeuXm1NU9xvhDxobY4v6TbxvCnfqLcw3Wicu1PxbZw7Z41dZOzTtA
qRLYrT_MfCoFPM7I_Ti8ZE5ABFmHn4PiiUNe1pw-9dUpkB593tPRN89VplpOh054Cd6IbI_0fpER
ahFifblNyy--eOfHGweuLAeebeY4fjSf2j0ti1ObU1JWNAQSMbmaHsjQ==>  for a chart
listing the fluid capacity of specific ZF/Hurth marine transmission models.
Not only should you run a good fluid, you should change it frequently. Let's
keep in mind that these Hurth gears don't have oil filters to trap sediment
and debris, so a short oil change interval is important.

AND

O Install a Flex Coupling. One of the best things you can do to protect your
engine/transmission is to install a flex coupling between the output flange
on your Hurth and the propeller shaft flange.

 

Before I had my Hurth transmission rebuilt I did consult Foley re. a
replacement. The recommended using the next size larger than the HBW-50 as
they felt that gear was on the borderline for the C320.  On investigation, I
found that the HBW-100 (or the ZF version of it,) is about ½ in. larger
fore/aft than the 50.  This means pushing the shaft an equal amount further
beyond the strut.  The recommended space between the strut and fwd hub of
the prop is 150% of the shaft diameter (1.5 in. for those with 1 in. shaft.)
Were I to do this I would also add a flexible coupling that would further
extend the shaft (I think.)  This further means removing the shaft, cutting
some off, re-fitting the coupling to the shaft (something a machinist should
do,) reinstalling it and realigning the shaft.  The $$$ kept adding.  

 

As the problem with my tranny wasn’t do to failure, I had a leaking seal, I
decided to have my Hurth rebuilt by a shop in Annapolis  for about $800.
That was maybe 4 years ago and 200 hours.  I’ve had no problems since then.


 

If you do rebuild or replace your transmission, it is recommended to also
install a new damper plate.  Maybe another $150.

 

Warren & Pattie Updike

1994 C320 #62 "Warr De Mar"