Re: Does this engine use a wasted spark ignition? - 1972 100HP Evinrude 100293
You should be able to use a standard tach with that motor. Tiny Tachs are great but they are more appropriate for an engine that doesn't have a rectifier/charge system.
If you open your control unit, you should find a gray wire that isn't connected to anything - that the wire that provides the signal to a standard outboard tach. On the back of the tach, there should be four posts - Send, Ign, Grd, Lt. Wiring is as follows:
Send: Attach gray wire from control unit.
Ign: Attach to purple wire on key switch.
Grd: Attach to suitable ground, switch panel ground is a good place.
Lt: Attach to switched side of running light switch, provides internal light.
The tach will also have a rotary type switch to set the correct number of pulses - I don't happen to know it off hand for this motor, but someone here will.
