Re: 1979 35hp tach
A Teleflex tach (or other fine brand) has 3 wires. One is for 12 volts positive, one is ground, and one is for the tach signal. That comes from the yellow/grey wire on the circuit board on the port side of the powerhead, which is from the rectifier, also mounted under the circuit board. Just run the tach signal wire to the screw that retains the yellow/grey wire.
