Re: OMC Tach ID

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July 14, 2015 at 9:50 pm #20158
Don
Participant

    US Member

    Art
    That tach has the grey lead meant for the alternator output of the 70s OMC outboards. The OMC stern drive tachs were run off the coil.
    So, this tach is for the outboard. There is no adjustment on this tach because back in the 70s only the 6 pulse alternators were used on the OMC outboards. So, this tach should work fine on your engine.
    Sorry, I don’t know any way of testing the tach, other than connecting it to see if it works. I’m thinking your engine has the water cooled regulator rectifier instead of the plain rectifier, but you could still wire this tach up temporarily on the terminal board where the grey lead is attached, simply ground the other lead. These early tachs did not require a B+ input to operate.