Thanks Rusty, that is the information I needed.. It's not the same
resistance and the Alpha Marine but at least they are both using linear
resistance to determine rudder position.

My ST5000 can operate without the rudder reference but has provisions for
it. My main objective is to be able to tell the control when the drive has
(or is nearly) fully extended..

As Larry was discussing, the ST5000 has a calibration routine in the set up
procedures. Hopefully this routine will settle for these resistances
differences from OEM. If not, the drive unit is very service friendly and
the pot could be changed out without much hassle. Alpha Marine is still in
business and may have a suiteable replacement or recommended source.

I don't know if any of you have ever seen a Alpha Marine linear drive, but
it is a very heavy duty unit.. Mine was built for external tiller use, is
weatherized and has a 18" total travel with over 1000# of thrust. (I don't
think I would want to get between the tiller and the cockpit coaming with
this monster) and 4 sec. stop to stop. This thing is really well built and
is fully field serviceable.
http://i6.ebayimg.com/02/i/01/4f/42/81_1.JPG
http://i14.ebayimg.com/02/i/01/4f/06/f5_1.JPG

Since this drive draws more current than an Autohelm drive, I am building a
secondary drive controller.

Thanks again Rusty, for taking the time to document those resistance
readings.

Steve
s/v Good Intentions