[C320-list] Hurth HBW50 transmission problem (and solution)

[kskis at aol.com]

Frank:  Sometimes you put a little work/thought into it and with some expert help it's "something easy".  Makes up for all the other times!  Good Work!  Neil Kornblatt  Harmony #973


-----Original Message-----
From: P.F. Ross <pfrstl at gmail.com>
To: c320-list at lists.catalina320.com TtS <c320-list at lists.catalina320.com>
Sent: Thu, Nov 5, 2020 9:55 am
Subject: [C320-list] Hurth HBW50 transmission problem (and solution)

I don't recall seeing this issue on the discussion list but thought I would
post it in case it happens to anyone else.

Thanks to current travel difficulties, we were far away from our boat and
it sat in the water unused for about 7 months.  Now back at the boat, I
went through my typical engine recommissioning tasks and let the engine
warm up in Neutral.

To check the drivetrain (boat was still tied to my dock), I shifted into
Fwd (engine at idle) and the engine immediately died.  I had already
checked the freedom of the prop shaft, but shifted back to N and checked
again, still free.

Checked tranny oil level, color and smell, all good.

A couple of more attempts and the same thing happened.  Tried Rev and same
thing.  It was obvious that the engine was being dragged down when tranny
was shifted into gear.

I tried again, this time slightly advancing throttle when tranny was
shifted.  I was able to keep the engine running slowly but now under
extreme labor.  Quickly shut down engine.

Checking the discussion list, I was looking at tranny rebuilds or
replacements for mucho $$$.  Well, darn (ok, worse).  There were several
online discussions on who to call, with mixed reviews.  One suggestion was
to call ZF (Hurth owner) directly so that is where I started.

My experience is mixed when calling large companies for help, but I cannot
say enough about Juan at ZF USA headquarters in Miramar, FL (direct line
954-441-4026).  He listened patiently to my situation and strongly
suggested that I was not getting enough travel on the Fwd-N-Rev actuating
lever on the side of the tranny case.  He advised to remove the actuating
cable and check.

The owners manual and overhaul manual (both on the 320 website) describe
minimum +/- 30 mm travel from N when measured at the lower hole (where my
cable attached).  While this measurement is kind of unwieldy, it is very
easy to feel the detents when operating the lever manually with the cable
disconnected.  Overtravel of the lever in either direction is not a problem
(according to manuals), but you need to make sure you are at least passing
the detents in both directions.

It was easy to make sure my actuating cable was free once it was
disconnected since I was able to push and pull the cable from the engine
compartment.  I made one very slight adjustment on the cable end threaded
pin to make sure I had plenty of Rev stroke (it seemed to be biased toward
Fwd) and reassembled.

Voila!  All is well and it now shifts normally.  I am not sure what, if
anything, the long slumber of my boat had to do with the problem, but my
thinking is that the manual exercising that I did to the tranny lever when
disconnected from the cable did the trick.

Hopefully I did not do any damage to the tranny when operating in the
half-actuated positions, but it does not seem like I did at least so far.
But it cannot be a good situation and one that it easily fixed, at least
for me.

Frank Ross
"Beta Wave" #206
Naples, FL