Re: tach on a 71 60 HP
I don't have a wiring diagram for a '71 60hp but you will probably find a yellow/grey wire coming from the rectifier, and a grey wire that goes from the terminal block into the wiring harness/plug. That grey wire is fed from the yellow/grey wire and will terminate in your control box, through the plug and control box wiring harness. If you have no tach now, the grey wire will be found inside of the control box, and won't be connected to anything. It should be used to provide the signal to the tach to display rpm. Be sure to wire the rest of the items on the tach properly - there should terminals for a ground, 12VDC from the key switch, 12VDC from the boat's lights, and the tach signal. Be sure to set the tach to the correct number of pulses for your motor.