I converted the Curtis PB-6 successfully for 3-wire operation using my pedestal throttle (cable)control. The electronics are now weather protected, and the mechanical element provides much better control.
After taking it apart, the Curtis had a 15K pot with 5K resistor wired as a 2-wire controller (requiring a reversing switch). I basically removed everything - the most useful part of the PB-6 is the lever attached to the pot (I'll post a picture). I drilled a new hole for the alignment peg on the pot (in the PB-6 it's offset about 30deg) so that when the lever is in the center of it's rotation the pot is a as well.
But now, contrary to my earlier post I need a pot which can go from full FWD to full REV in about 90degrees of rotation. A 10K pot was needing about 180. I made a lucky guess that the controller didn't actually need 5K of resistance (the mid-point of the 10K pot) - it actually just measures the difference in resistance between either side. So I put a 5K pot in and that gave just about exactly the right range. I did decide to offset the range (by adjusting the lever on the pot shaft) so that full rev is only about 30amps - that gave 80amps for fwd (playing with different pot values might be a future option). My normal cruising speed is 40amps.
Other than a minor mishap where I forgot that my throttle had 2 directions (what was full off is now full-steam ahead...) - works great. The final tweak is to rig some sort of mechanical detent for the mid-point of the throttle - I just have it marked for now.
Thanks for everyone's help in figuring this out!
-Keith
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