Its probably an electrical connection tween the battery and the motor.
When all else fails, use process of bypassinization,.....12v hot wire directly to the motor,.....reverse polarity to reverse rotation.
Rich
'01 31' Rexall Vision, Generac 5.5k, 1000 watt Honda, PD 9245 conv, 300 watts Solar, 150 watt inv, 2 Cos 6v batts, ammeters, led voltmeters all over the place, KD/sat, 2 Oly Cat heaters w/ ox, and towing a 2012 Liberty, Lowe bass boat, or a Kawi Mule.