From the "knife" connectors inside the rubber tubes at the back of the engine with an ohm meter, 4.6-5.4 resistance on each wire. If the shift wire to the drive is cut in any way it has to be changed by dropping the lower section of the drive. The bolts that hold the swivel bearing usually want to break off so have a torch ready.
If the reverse clutch is broken , it can be replaced without removing the drive. Remove the 4 slotted screws and pull the seal cap off. Very carefully pull about 2" of the wire out and cut it about 1" from the coil. Remove the snap ring, gently push the upper cut wire just inside where it can be pulled back. Install 2 of the screws into the magnet and pull it out, them grab the reverse gear and pull it out to replace the spring, Use a butt connector to repair the cut wire or solder with shrink wrap after re assembly.