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Results 1 to 7 of 7
  1. #1
    Join Date
    Jul 2011
    Location
    East Troy Wisconsin
    Posts
    3

    Default 1976 Merc 650, 65hp 3Cyl INTERMITTENT SPARK

    1st off, i want to thank ANYONE who can give me some insight on this.
    Its a 1976 Mercury 650 / 65hp Triple with the Thunderbolt Ignition.
    ill give you everything i know, and everything ive done. Im pretty "Tech savvy" being a 20yr harley/powersports tech myself, HOWEVER, these are a whole new animal...anyway, im at a dead end here...and as you would do if you needed a Harley questions answered, im lost when it comes to these things thus i come to those who know a TON more about these than myself, so again... THANK YOU!!

    thus far, Ive checked fuel, good
    eliminated the connection at the motor and ran fuel line directly to the fuel pump @ the motor good
    when it runs, it runs litterally FLAWLESS, doesnt miss a beat!
    Ill run for 15 seconds some of the time, and for 4 hours other times.
    The mercury switch is GONE
    ive replaced the Power Pack/ECM
    bypassed the "white" wire on the ecm directly to the battery to eliminate a bad ignition switch
    replaced the trigger/distributor
    replaced a stator
    tested the regulator/rectifier
    cleaned and checked EVERY ground including the ones on the boat itself just for good measure
    replaced the coil
    has a brand new fully charged battery

    when it runs, itll go for whatever period of time it feels like it, and then shut down as though someone turned off the key,
    and not start back up for 10 minutes to 5 hours to 3 days, and on several occassions ive double checked to make sure it actually had no spark and wasnt a fuel issue...

    with everything ive done this far, it reacts exactly the same...
    i also left the cap OFF the fuel tank to reassure it wasnt hydro-lock or the fuel being suspended from a non venting cap

    and again, when it runs, it runs PERFECT, but only runs intermittently.....and its not every day...some days itll run every time i try it, sometimes itll go 3 days before it run at all while trying it on a daily basis... i am SO confused!

    Any insight would be emormously appreciated ... thank you SO much!

    Mark

  2. #2
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    12,074

    Default Re: 1976 Merc 650, 65hp 3Cyl INTERMITTENT SPARK

    Mark:

    When it won't run, does it have spark?

    Jeff

  3. #3
    Join Date
    Jul 2011
    Location
    East Troy Wisconsin
    Posts
    3

    Default Re: 1976 Merc 650, 65hp 3Cyl INTERMITTENT SPARK

    no, in fact ive checked several times when its quit running just to make sure

  4. #4
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,181

    Default Re: 1976 Merc 650, 65hp 3Cyl INTERMITTENT SPARK

    Assuming that the boat engine's wiring is original there could be a +/- wire in the ignition circuit that is corroded internally and loses continuity from vibration. I and some others have found the culprit by pulling, bending and tugging on ignition circuit wires while the engine is running.

    Edited from another post of mine.

  5. #5
    Join Date
    Jul 2011
    Location
    East Troy Wisconsin
    Posts
    3

    Default Re: 1976 Merc 650, 65hp 3Cyl INTERMITTENT SPARK

    now that i havent done, ill have to give that a shot and post what happens.. Thank you

  6. #6

    Default Re: 1976 Merc 650, 65hp 3Cyl INTERMITTENT SPARK

    I have the same prob did u get it figured out yet???

  7. #7
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    12,074

    Default Re: 1976 Merc 650, 65hp 3Cyl INTERMITTENT SPARK

    I'm confused: Has it got spark or not?

    Jeff

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