1977 johnson 70EL77S tachometer wiring

[turbofn1]

Looking for tachometer wiring specs. I have an 1977 johnson 70EL77S motor with OMC tachometer p/n 172927, when checking (marinengine .com), in 1977 accesories, says this tach is compatible, has 4 wires out, black/gray/blue/brown, pretty sure black is negative, gray is tach lead, wondering what blue and brown are for? I have a wiring diagram, doesn't mention any wires except gray, would appreciate any info, thanks

 

[metriccrescentwrench]

Re: 1977 johnson 70EL77S tachometer wiring

Most outboard tachs have 4 connections. "I" gets 12 volts from the ignition switch, "G" is ground, "S" gets the tach signal, and "L" gets 12 volts when the boats lights are on.

Normally the tach signal is a grey wire, +12 from the ignition switch is purple, ground is black. The others I can't recall off the top of my head, try doing a search for outboard engine wiring color codes.

 

[F_R]

Re: 1977 johnson 70EL77S tachometer wiring

Blue and brown are the illumination light.