=1970 4 HP Mercury Changing the white insulator

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  • August 28, 2023 at 1:52 pm #279878
    outbdnut2
    Participant

      US Member

      I got a new white insulator for the points on the 1970 4 HP Mercury I posted questions about a couple weeks ago.  Where the wire connects to it, there appears to be some high-voltage insulating stuff glopped over the screw head and the connector on the wire.  I used to have some paint-on stuff called “Carona Dope” that insulated thousands of volts for stopping high voltage leaks on old TVs with picture tubes, but that is long gone.  I see that I can still buy that stuff on Amazon, and I’m sure it will work, but was wondering before I order it – What do you use?

      Thanks,

      Dave

      August 28, 2023 at 2:23 pm #279880
      seakaye12
      Participant

        US Member

        From what I have read;  Corona Dope is one of the best products of it’s kind.  I would use that but not sure if it is actually necessary in that application. 

        August 28, 2023 at 3:26 pm #279883
        jeff-register
        Participant

          US Member - 2 Years

          I have used Super corona dope on hi-voltage transformer leads like magneto terminals & works well. You might look up MG Chemicals on  line for insulating paste that would work better. MG also sells Super corona dope at a better price as they make it. Check it out please, they have all kinds of coatings for electronics apps.

          August 28, 2023 at 5:12 pm #279884
          outbdnut2
          Participant

            US Member
            seakaye12 wrote:

            From what I have read;  Corona Dope is one of the best products of it’s kind.  I would use that but not sure if it is actually necessary in that application. 

            Yes – I don’t know if that glop of insulating stuff is there to prevent arcing of the 600 or so volts that gets sent to the ignition coils, and/or if it’s there to keep dirt and moisture off the connection. It could be there to keep someone from touching it, but not likely because of its’s location well under the mag-plate where it would be difficult to touch while the motor is running.

            Hey – I found I have an unopened bottle of GB Electronics “Liquid Tape” with a brush in the cap. I looked it up and it is rated to insulate at 1400 Volts /mm, and seals out moisture, rated to 200 degrees. That should be plenty for this application – maybe 2 coats. I’m going to try it….mainly because I have it! If it electrically breaks down, I’ll get the Corona Dope.

            FYI – I’m putting on a new wire because insulation on the old one is starting to crack (common old Merc problem). I have some stranded, tinned, wire rated for thousands of volts for use in florescent light fixtures. That should seal the voltage!

            Thanks again for your replies!
            Dave

            September 2, 2023 at 6:43 pm #280095
            outbdnut2
            Participant

              US Member

              Follow up: I’ve got it running great now!

              – Changed the white insulator and used GB Electronics Liquid Tape to insulate the wire connection.
              – Changed the ignition coil which had an open secondary – swapped in a different color coil from a couple year newer 9.8 parts motor. Had to scrape paint off the motor’s coil mounting surface below the coil because the ground wire came out the opposite side.
              – The choke plastic link from the choke knob to the choke detail was worn bad so if you turned the knob slightly beyond the choke on or off positions, the knob came loose. The worn link the knob attaches too is discontinued, and different length in my parts motor. I drilled and tapped two holes near the choke knob and put short 1/4 x 20 machine screws with big heads in so the knob hits these in both directions, limiting its travel so it can’t come apart from the link inside. This worked very well! Photo below. Choke knob label missing, so I made one.
              – As with most old motors that haven’t been run for a while, I had to replace the impeller.

              Thank you all for the help diagnosing the ignition system.
              Dave

              Merc-Choke-limit-screws-1

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