[C320-list] Linear autohelm

[Greg Arnold]

   I also am thinking about making the upgrade to a Raymarine below-deck
   linear drive.  There is quite a lot of info on this topic on both the
   320 Association site (including pictures) and in the Google archives of
   the 320 discussion group.
   The most popular mounting location for the Raymarine linear drive seems
   to be above the little door on the athwartship bulkhead that separates
   the aft cabin from the lazarette area.  Has anyone had any problems
   with this location?  On my boat, this bulkhead has a thickness of only
   1/4", and does not appear to be designed to carry any structural
   loads.  Also, this location restricts the length of the tiller arm due
   to lack of space between the bulkhead and the rudder post.  The
   shorter-than-recommended tiller arm adds stress to both the autopilot
   and the bulkhead.
   Other Catalinas such as the 380 and 400 mount the drive beneath the
   swim step.  This doesn't work on the 320 because it puts the drive too
   low.  However, around serial number 380, Catalina shifted to a new 320
   deck mold that put a seat on both sides of the swim step.  I would
   think the drive could be mounted beneath that seat on the starboard
   side, with the drive extending forward to the tiller arm on the
   starboard side of the rudder post.  A local 320 owner who drilled this
   seat for a stern anchor roller says the seat is balsa-cored, which
   means it should be quite robust.
   The problem with this below-seat location is that the Raymarine Type 1
   drive is not long enough to extend from there to the tiller arm.  That
   is fixable at a price of several hundred dollars by using the Raymarine
   Type 2 Long drive, which appears to fit perfectly.
   One advantage of the below-seat location with the Type 2 Long is that
   you would be able to use a full length tiller arm.   Also, the Type 2L
   has a 16" rather than 12" stroke, which will eliminate any steering
   restrictions of the shorter Type 1 drive.
   Raymarine says the electronics of the ACU-200 are not robust enough for
   the Type 2, instead you must use the (very expensive) ACU-400.  This
   makes sense if you have a big boat that requires the Type 2.  However,
   the Cat 320 should not place any more load on the Type 2 than on a Type
   1, so I don't think you would need to upgrade from the ACU-200 to the
   ACU-400.
   Interesting facts learned by looking at the autopilot posts on
   forum.raymarine.com:  The Type 2 Short is identical to the Type 1
   except for motor size (so, depending on how you look at it, the Type 2
   does not have a more robust construction than the Type 1, or the Type 1
   shares the robust construction of the Type 2).  And the Type 2 Long is
   identical to the Type 2 Short except for stroke length.  So the Type 1
   and Type 2L are identical except for the 2L's larger motor size and
   longer stroke.
   One final point: under-deck pilots are really expensive.  The Type 1 is
   $3700, plus you need a $600 tiller arm.  Add sales tax, and you are
   around $4500.  That doesn't include installation, which a local boat
   guy says will be more than 20 hours and may be 30 hours (at $100 per
   hour).  You are looking at a price of around $7000, so a few hundred
   dollars more for the upgrade to the Type 2L drive is just pocket
   change.
   Greg Arnold
   Santa Barbara, CA
   2005 C-320 #1054

   On 8/20/2022 4:59 PM, surprise thompson87.com wrote:

I think my boat was one of the first to convert to a below decks linear drive fr
om Raymarine. Pictures of the install are in my owners gallery folder. (“Surpris
e” #653). This was the best upgrade I’ve made to the boat. Highly recommended.

Scott Thompson



On Aug 20, 2022, at 5:50 PM, John Meyers [1]<jcmeyers7 at gmail.com> wrote:

I am thinking about putting in a linear autohelm. Haven't been on a boat
with it. Not finding much written about this especially on the 320 unless I
am looking in the wrong place.

Any advice? Go for it? Avoid it? Which brand/model is good?

Thanks

John Meyers
Muskegon, MI
WInd Chime
1997 #406

References

   1. mailto:jcmeyers7 at gmail.com