MerControl Problems … Maybe?

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    Ed@deathwish-outboards

    US Member - 1 Year
    Replies: 13
    Topics: 1
    #205015

    I’m trying to help someone with his MerControl. Every time he starts the motor ( a 1976 Merc with at least 3 cylinders, I’m still getting that info.) He gets an 18v shock from the controls. He has replaced the trigger, switch box and rectifier. When it does start the top two cylinders misfire. When I get more information I will post it. I am thinking It is not the controls but the motor. Thanks ED

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    billw

    US Member - 2 Years
    Replies: 1219
    Topics: 39
    #205018

    There are two ground straps that are supposed to connect the lower cowl to the engine block. If those are not there and you have stray spark plug voltage leaking, that’s one way to get shocked. Another is if you have an engine with ADI (Alternator-Driven Ignition) or a CDI distributor system, you have a couple of hundred volts in the key switch, waiting to be grounded out when you turn off the key. If you have a bad key switch, a lot of corrosion in the box, or wires with bad insulation (very common in that era of Mercury) you will get zapped from the box. Both of these scenarios can explain the engine misfire, as well.

    Long live American manufacturing!

    • This reply was modified 1 month, 1 week ago by Avatarbillw.
    • This reply was modified 1 month, 1 week ago by Avatarbillw.
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    Ed@deathwish-outboards

    US Member - 1 Year
    Replies: 13
    Topics: 1
    #205056

    He said he “cut wire in control for rpm and no more voltage leaks at box.”

    I didn’t know there was such a wire unless it was an aftermarket hookup.

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    dave-bernard

    US Member - 2 Years
    Replies: 1129
    Topics: 14
    #205057

    yes it goes to the plug in the front of the box.

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    billw

    US Member - 2 Years
    Replies: 1219
    Topics: 39
    #205058

    For 1976 model year wiring, it seems strange that he cut the tach wire and, I am assuming, he also stopped the cylinder misfire? There is seemingly no connection between the two, unless somewhere in the box or harness, there was a short between the stop circuit and the tach circuit. I am pretty sure that year had an alternator driven (common type) tach and not an ignition-driven one. I gotta go look at a diagram, now….

    Now if, like many Merc owners, his engine is about ten years older than he thinks, that’s a different story.

    Long live American manufacturing!

    • This reply was modified 1 month ago by Avatarbillw.
    • This reply was modified 1 month ago by Avatarbillw.
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    Ed@deathwish-outboards

    US Member - 1 Year
    Replies: 13
    Topics: 1
    #205498

    A new stator seem to have taken care of the misfiring cylinders

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