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1983 50HP Bad Coil?

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  • 1983 50HP Bad Coil?

    We took our boat out today and it was running great. We stopped for ice cream and when we went back out I noticed it didn't seem to be running right. So I did some trouble shooting.

    I pulled the bottom plug wire and the engine died immediately. I pulled the top wire and it kept running. When I pulled the wire I immediately heard it arcing. I looked and saw the top coil arcing from the bottom of the coil tower to the block.

    Is this a bad coil? Plug wire?

    Before I put the boat on the water I had checked spark and had good spark on top and bottom although the top seemed not quite as strong as the bottom.


  • #2
    Re: 1983 50HP Bad Coil?

    When you pulled the wire you forced the voltage to find a path to ground. It sounds like you have a crack in the coil, I have seen the same thing happen, but the coil would not arc to gound when the wire was on the plug and the engine ran fine.
    It sounds like you have spark to the cylinder, have you checked fuel delivery and compression?

    Comment



    • #3
      Re: 1983 50HP Bad Coil?

      I just rebuilt the carbs and the compression was checked at the same time, 120 on both cylinders.

      It ran great for the first 20 minutes. It didn't act up until we stopped for a bit and then went back out.

      What is the best way to check fuel delivery?

      Comment



      • #4
        Re: 1983 50HP Bad Coil?

        You can use a spray bottle with fuel mixture in it and spray directly into the carb.
        Have you tried checking the spark with an air gap tester set to 7/16"?
        If you have a coil that doesn't pass the spark test, swap the wires from the power pack to the coils and see if the no spark moves to the other cylinder, maybe you have a power pack going out.

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        • #5
          Re: 1983 50HP Bad Coil?

          Originally posted by Daviet View Post
          Have you tried checking the spark with an air gap tester set to 7/16"?.
          I did after rebuilding the carbs and before putting the boat back on the water. Both cylinders arced across about 1/2" but I do remember thinking the top cylinder didn't seem quite as bright as the bottom.

          I haven't checked it after today's problems as I didn't have any tools with me.

          Unfortunately I can't get it home right now as the hitch on my truck is out of commission.

          Comment



          • #6
            Re: 1983 50HP Bad Coil?

            We got the boat home and I was doing some troubleshooting today.

            120PSI on both cylinders, nice blue spark on both cylinders. Top coil still arcing against block when plug wire removed. I found the crack in the coil so I've ordered a replacement from here.

            Again I noticed I can remove the top plug wire while it's running and it affects the engine but it doesn't die. If I remove the bottom plug wire it dies instantly. Obviously my top cylinder isn't running up to par.

            When I redid the carbs I replaced the fuel lines and I've noticed the fuel line running from the split to the top carb seems to be kinked where it has to bend 90 degrees to connect to the carb. I'm thinking this could be my issue with the top cylinder not running as strong.

            My question is this: what's the best way to correct that? Make that section of fuel line longer or install a 90deg fitting in the line?


            Thanks,

            Gary

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            • #7
              Re: 1983 50HP Bad Coil?

              Either way would work. I think the factory lines were formed with a 90 degree moulded into them.

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              • #8
                Re: 1983 50HP Bad Coil?

                Originally posted by Daviet View Post
                Either way would work. I think the factory lines were formed with a 90 degree moulded into them.
                That explains the nice 90deg bend on the lines I took off. I may end up having to lengthen the line, can't seem to find small 90deg fittings.

                Comment



                • #9
                  Re: 1983 50HP Bad Coil?

                  Find an exploded diagram of the motor online and get the part number of that piece of fuel line. Then put that number into a search engine, you'll be surprised how many used parts are available.

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                  • #10
                    Re: 1983 50HP Bad Coil?

                    Good idea, but that defeats the purpose of replacing the fuel line; replacing non-ethanol resistant fuel line.

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