OMC Tachometer

[Frank Acampora]

Stripping out my 1973 Glastron Gt 150 in prep for restoration. It came equipped with an OMC tach for a 1970s (assuming 1973 also) electric shift Johnson 65. (could be a 60 hp, hood has been changed because Johnson colors match the boat) Tach has no numbers. Four wires enter the case in the rear: Black, Grey, Purple, and Blue. I am assuming black is ground as on most boats.

Which wire is power and which wire is signal? Since there is no terminal for lighting, I am assuming that one of the four wires is the power to the light. Which color is that one?

Thanks in advance-------Frank.

 

[ezmobee]

Re: OMC Tachometer

Purple is ignition switched positive. Gray is pulse. Blue must be lighting or something.

 

[steelespike]

Re: OMC Tachometer

BIA colors beginning c. 1970s Gray is the signal,purple 12 volts from key switch.
blk indeed is ground.

 

[boobie]

Re: OMC Tachometer

Blue is for lighting.

 

[Frank Acampora]

Re: OMC Tachometer

Thanks again, fellas. Now I just need to test it.