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  1. #1
    Cadet
    Join Date
    Jul 2010
    Location
    Hensley, Arkansas
    Posts
    16

    Default 1977 Mercury 500 Thunderbolt 50HP engine harness and wiring harness rebuild

    My wiring harness is shot. While trying to test for a shot in the key switch insulation was falling apart as well as the wires just breaking. I cut everything loose from the key switch which tested fine but looks like it is 30 years old (which it is) so I will replace it with a new push to choke key switch. I started cutting back the wiring harness to find good wire but I dont think there is any. Just wire skeletons/remains. The harness is $230 (http://www.iboats.com/Wiring-Harness...view_id.174724) I previously rebuilt the engine side wiring harness and at that time considered just building it all from scratch getting rid of the engine and the wiring harness. Any gotchas to doing that? Looks straight forward. Just home runs for each wire to the switch as follows per the attached diagram.

    Red Solenoid to key position A
    Black Solenoid to key position D
    Orange Switch box to key position E
    Yellow Solenoid to key position B
    White switched power from key position F used by the choke and other keyed accessories
    Gray Choke Solenoid to whatever that is on the new push to choke key switch
    Brown unused as I dont have a tachometer

    Thanks

    Mike
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