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4 hp evinrude 1976 4606m

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  • 4 hp evinrude 1976 4606m

    i have been through this motor from tank through carb. Put on new condensers, but after running for 3.5 hours, one of my twin cylinders quits.
    As it was acting up, I pulled the plug wire off top spark plug , and there was no change.
    This motor runs great , idles purrrfect , starts first pull, but after 2-3 hours, I loose a cylinder.
    Is it obvious that a coil is going bad , after 3 hours?
    Am I missing something?
    thank u in advance.

    And btw I pulled the plugs and they are wet, oily

  • #2
    Have you tried new plugs or swapped the existing ones over to check if its a dodgy plug ?

    If not plugs, and you have fitted new condensers, have you checked/ gapped points ?

    If not plugs or points then suspect coil. Inspect them. If one is not obviously defective you could swap the two over to check.

    If both plugs are wet with fuel and oily maybe the carb is flooding .. Presumably you are using 50:1 fuel mix with a TC-W3 oil

    Correct plugs ? Should be Champion J6C, gapped at 0.030" ( NGK B6S are equivalent)


    • #3
      my vote is a coil swap ….. if same condition … then swap the condensers both items which heat can affect

      finally … with cheap chineese coils… I would redo all electricals a-z

      p.s. keep all coil wires away from moving parts like…. crankshaft and flywheel :-)



      • #4
        Remove the top coil and inspect for " burn through " and shorting to the mag plate.--------Or as a test close up the plug gap on the top plug to 0.020" as that reduces voltage demand to jump that gap.------Agreed it is likely a coil failing.
        Last edited by racerone; October 8th, 2019, 09:04 AM.


        • #5
          Okay today I checked to make sure plugs were both getting spark, and they are.
          Although no matter what amount of time I ran it, the plugs were both soaked.

          The top cylinder still isn’t firing though. Occasionally it will pick up for a few seconds.
          I did notice gas leaking from my high speed adjustment needle. ( slow drip)
          Does it make perfect sense the problem is within my carb?


          • #6
            No it does not seem like you have a carb problem. The carb feeds BOTH cylinders. No way can it feed just one. But it could be set too rich, which will foul plugs. If it is, simply adjust it. Drip can be fixed by tightening the packing nut a bit.

            A bad fuel pump diaphragm can cause flooding of whichever cylinder it is mounted on. But it wouldn't fix itself for 3 hours.

            Still points to an ignition problem.


            • #7
              Logic usually saves us time but does not always work because it stops our progression to happiness :-)

              you have no choice but to proceed with progressive component swaps or... replacements
              most suspect being coils and condensers

              you did not write much about your coils & their condition (, ohm values , new, old ,cracks, burn marks etc...)

              what about wires ( original brittle boot clips recrimped) )

              see "magneto section" in the Leroy article


              keep at it… that little kicker should purr all day long and night

              patience brings joy


              • #8
                After 3 1/2 hrs run time, maybe the motor is over heating (could be due for a new impeller). Having said that J&E, Sierra and CDI coils are pretty reasonable. Fully rebuilding the magneto is likewise pretty reasonable for your motor. (include condensers, points, solid core 7mm wires (not automotive wires). New clips and boots.

                But check operating temp. Surface temp of the top of the head shouldn't be too hot to touch.


                • #9
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                  1976 evinrude 4 hp 4606m

                  Now I have acquired2 armature plates

                  I am thinking of converting one into electronic transionized ignition. And do away with points and condensers.

                  Any dos or don’t s? Thank u in advance