I think bass pro or Cabelas sells a setup to have foot pedal for hand control. Doubt though it would work with yours since the shaft on those old motors is awful small compared to today's motors. That old motor has no power to speak of and they draw a lot of amps for power delivered. You would be far better off checking Craigs list or pawn shops places like that to find a inexpensive foot control later model motor. Just had a flash. PM Shipahoy. He just got a old boat he is restoring and if I'm not mistaken he was replacing one of those late60's shakesper got control motors. If you are wanting to stay with old stuff on the boat you are fixing up.
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Charlie Weaver USN/ENC 1965-1979