describes C34 owners' Autoprop upgrade projects.
Also see Autoprop articles by Rick Hildahl,
Attitude Adjustment, 1989 C-30 #5630, Ballena Isle, CA (SF
Bay) AND Steve
Ritter - Night Flyer #687 just below this one!
Autoprop article......C-34 Projects Page
By Bob Kovich, Catalina 34 #1424 'Big Dog', Port of
Sheboygan, Wisconsin, email@example.com
Click on any Picture to Enlarge
I have a slightly different take on the installation and
operation of the Autoprop. I purchased an Autoprop in spring
of 1999 and had my boatyard install it. They also ran into
trouble when running the blades through the 360-degree swivel
that they must do for reverse. The blades would hang up on the
strut and refuse to rotate. They called Steve Armitage at
Autoprop and was told there were two solutions to the problem.
1. Install a flexible Drivesaver between the engine
flange and the propeller flange, which would extend the shaft
out through the hull about an inch. This would give the
Autoprop enough clearance to rotate freely. The problem with
this solution is that every time you extend the propeller away
from the cutlass bearing you increase the potential for
vibration. Also because the Autoprop is about 3 times heavier
than the standard Michigan Wheel three blade 15 X 9 propeller
it was replacing, there could be increased stress and wear on
the cutlass bearing.
2. Grind away at a portion of the bronze strut enough
to allow the Autoprop to clear. The potential problem with
this approach is the weakening of the strut and the
catastrophic failure of the strut, propeller shaft and
propeller. Despite the potential problems I choose option #2
and had the yard grind out enough of the strut to allow for
1/4 inch of clearance for the Autoprop. (See photos)
After one year of operation I find no problems with this
approach. There is still plenty of support for the shaft and I
don't have any vibration when motoring or sailing. There has
been no appreciable wear on the cutlass bearing. The extra
control and lower RPM when motoring was impressive but it is
the change when sailing that really makes the Autoprop Pay
off. In light air of 8-12mph true, I can see as much as a
3/4-knot increase in boat speed. Once the wind builds to 15+ I
am moving pretty much at hull speed and the Autoprop becomes
You do have to get used to putting the transmission in
forward, not reverse, to lock the shaft and allow the Autoprop
to correctly feather into the water when sailing. I don't have
any problems with the shaft rotating when locked in forward.
It is fun to informally race some of my friends when the
transmission isn't in forward and the Autoprop isn't
feathering. Putting the transmission in forward locks the
shaft and the Autoprop feathers, which allows me to pull away
just like kicking into overdrive.
I will keep the group posted on the status of the bite out
of the strut to see if there are any failures down the road
but things are looking good so far into year two.
Bob Kovich, Catalina 34 #1424 'Big Dog', Port of Sheboygan,
Autoprop article.#2.....C-34 Projects Page by
Rick Hildahl, Attitude Adjustment, 1989 C-30 #5630,
Ballena Isle, CA (SF Bay)
This weekend I installed an Autoprop on my '89 Catalina 30. I
chose the route of adding the Drive Saver between my
transmission and driveshaft instead of modifing my strut. I
went this way mainly because I didn't want to haul out just to
change props. I was able to swap them while free diving (one
breath at a time!)
These are 8 benefits I received by using the Drive Saver
instead of cutting my strut:
1. No haulout necessary.
2. No modification to hull or strut is necessary.
3. Additional 1 inch clearance from strut gained by
moving shaft aft.
4. I also gained additional prop tip clearance from the
5. The engine/transmission are now electrically
isolated from the prop and shaft (less electrolysis).
6. The rubber bisket absorbs minor vibrations for
7. The Drive Saver will break before any other part of
the drive system in the unlikely event the prop were to hit
something and suddenly stop.
8. Because the Drive Saver flexs, flange alignment is
After I gain more experience with this setup I can decide
if moving the prop aft does create other problems. If it does
then I can always undo this modification during the next haul
out and then try notching the strut.
Rick Hildahl, Attitude Adjustment, 1989 C-30 #5630, Ballena
Isle, CA (SF Bay)
Autoprop article.#3.....C-34 Projects Page by Steve
Ritter - Night Flyer #687
I installed an Autoprop just prior to my trip to the
Bahamas and wanted to let you know my impressions and
problems. It's unscientific and I really don't know a way to
check the sailing performance increase, but I think I'm doing
better than one kt difference in wind speeds of 5-10 kts. This
was borne out by a 335nm passage from Man of War Cay to
Fernandina Beach in 65 hrs, all but 14 under sail in light
winds. My previous best was 72 hrs in a stiff breeze.
Naturally, in winds above 15kts little speed increase was
noted since the boat was approaching hull speed regardless.
Under power, I'm getting about 6.7 kts at 80% of max rpm, and
approach hull speed at max power. I'm very pleased!
There are some glitches, however. When I initially
installed the prop, the prop would contact the cutless bearing
strut when the prop reversed and the blades swung forward, so
to increase clearance I installed a Drive Saver which
positioned the prop 1" rearward, which was enough by
1/4". The only other problem so far is shaft rotation
under sail above 3kts boat speed, which (naturally) gets
faster at higher speeds. This occurrs regardless of whether
the transmission is in reverse, forward, or neutral, and has a
dramatic effect on boat speed since the prop won't fully
feather if it's rotating. I'm presently using Vice Grips on
the shaft to secure it under sail, which is obviously not
suitable. I'll have to install a shaft lock which can be
controlled from the cockpit before my anxiety level about the
situation will be under control!
The people at Autoprop are excellent. My first prop lugged
the engine, so they really hustled to fire out another smaller
one before my trip, and basically said get the first one back
to them when I could!
As time passes, I'll let you know of problems with
maintenance, fouling, etc. So far I'm ecstatic with the
increase in performance! (Steve
Ritter - Night Flyer #687)
Important: The opinions expressed here are those
of the individual contributors to this page, and not those of
the Catalina 34 National Association or Catalina Yachts, Inc.
Additionally, this material has not been reviewed by Catalina
Yachts, Inc. for technical accuracy. This page's maintainer
cannot guarantee the accuracy of this information or the
desirability of suggested modifications or upgrades. Please
obtain assistance from a competent marine mechanic or boatyard
prior to making any significant modifications to your vessel.