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  1. #1
    richard cruthis's Avatar
    richard cruthis Guest

    Default i have an old house boat. it h

    i have an old house boat. it has the old 270 hp 350 mercruiser w/outdrive. wanting to put in an rpm guage in the upper station. i found out that it takes a special tach for the old thunderbolt 1 ignition. the tach uses a negetive pulse. all other tachs that i can find use a positive pulse. is there anyone out there that has a suggestion or may have an old tach that would work that they may want to sell?

  2. #2
    Join Date
    Jul 2006
    Anderson, South Carolina,

    Default "Richard, Every Tach I'


    Every Tach I've ever seen is triggered by the negative pole on the coil. Someone correct me if I am mistaken.

    follow link, see diagram and description;link2=1050"

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