I have replaced the rectifier with 2 used ones and the tach still don't work.. I have 2 motors so I took the working tach and hooked it up to the motor that the tach didn't work.. It still don't work.. I have verified that both tachs are good but don't know if my rectifiers are good or not. I hooked up the tach at the motor, red to ignition, black to ground, and grey to pull.. Still nothing.. I didn't cut the gray wire at the connector when I did this ,I just made the wire bare and tapped into it.. Volt meter reads 12 volts with ignition on and don't change when the engine is running.. The motor serial numbers are gone but I was told it is a 1990 or 1991 model.. The rectifier is bolted down with 6 bolts and has 5 wires, its on top of the engine and covers a water passage.