Re: tohatsu 9.9/18, wont shut off
Having the exact model would help. It's probably a 9.9/15/18 B (or B2) EP, which is electric start, remote control. Those motors are magneto-type ignition, not battery type, so cutting 12v will not turn off the motor. The ignition stop is done by grounding the brown wire to the black frame ground wire. This can be done at a stop switch on the lower cowl (if so equipped), at a stop switch at the RC box, or via the key switch (if key start, which is usually the case). Armed with a good knowledge of low-voltage wiring, your good-quality analog ohm meter, and the Factory service manual, Part# 003-21041-0, available for $40.00 from any dealer (including me), it should be pretty straightforward to diagnose the problem area. You may have a disconnected or corroded brown wire/connector anywhere along the way from the CD to the key switch, or may have a bad key switch. Does the motor stop when pressing the red stop button at the RC box? If so, you have good continuity to the box, and can troubleshoot the internal RC box electrics (including the key switch)... if not, the problem is between the RC box and the motor's internal harness.
