tach wiring

[smike26]

Installing original tach. From shift box i have black white and green. At tach I have blue gray red and black. Please advise how to hook up.<br />78 Merc<br />Thunderbolt ignition<br />115hp inline 6

 

[studlymandingo]

Re: tach wiring

Black is the ground, one of the wires (My guess the blue) goes to the light. The remaining wire will be the sending unit from the ignition system.