I picked up an old electric boat that has the sliding reostat type speed controller that works of the servo. It only will run the motor in forward and does not seem to kick in at a very low speed. It will also not run in reverse. I have check and cleaned all the contacts. Could the coil thing be bad? Anyone know where I could find a new or good working used one? The boat is an old Playtron Candy running a 7.2v Nicad.

Thanks