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OK, You guys are smart - 3/8 to 8mm adapter

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  • OK, You guys are smart - 3/8 to 8mm adapter

    I want to use a Teleflex shift knob on a Yanmar engine control lever. The hole in the Teleflex knob is threaded 3/8-24 and the Yanmar lever is threaded 8mm.

    Any ideas for how to make an adapter? I tried making a bushing with a 3/8 outside thread and an 8mm inside thread, but there doesn't appear to be enough wall thickness.

    Any clever ideas?

  • #2
    Can you drill out the middle of the shift knob to allow a new insert that can be threaded inside for the 8mm? I don't know how much extra material you have to work with in the knob.

    If need be you can drill either side perpendicular to the insert to place small set screws to keep it set in place.
    Last edited by Fisherlady2; 05-29-2021, 01:13 PM.
    Karen
    Punxsutawney, Pennsylvania
    1986 Shamrock H/T with RWC 330 hp PCM, dual hydraulic helm
    1992 Mako 211CC w/Mercury Optimax 175
    3 other smaller OB boats and a trusty old canoe...

    Comment


    • #3
      Maybe this...?


      https://www.mcmaster.com/91646A125/
      1986 26' HT w/5.7 PCM 330HP RWC

      Comment


      • #4
        Sorry, I've had too much think time lately, looks like radiomans option is simpler.
        Karen
        Punxsutawney, Pennsylvania
        1986 Shamrock H/T with RWC 330 hp PCM, dual hydraulic helm
        1992 Mako 211CC w/Mercury Optimax 175
        3 other smaller OB boats and a trusty old canoe...

        Comment


        • #5
          Originally posted by radioman View Post
          Just what I was thinking or maybe this
          https://www.mcmaster.com/knobs/threa...hread-size~m8/
          '78 20ft Cuddy
          Mercruiser 350 FWC preVortec w/Carb

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          • #6
            Fill it with a weld slug. or even J_B aluminum weld, and re-tap?
            1987 26' Hardtop
            1996 20' Walkaround Cuddy

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            • #7
              Grease up the shaft threads, add jb weld or other epoxy to knob treads and insert. When set up you should have threads that work.

              Just wishin', and hopen', and dreamin'

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              • Ship
                Ship commented
                Editing a comment
                Times two!!

            • #8
              Gentlemen-

              Add shipping, tax or whatever fee you want to. Less than $20 bucks from McMaster and you will get it in a day or 2. And just screw it on. WTF
              '78 20ft Cuddy
              Mercruiser 350 FWC preVortec w/Carb

              Comment


              • crhodes
                crhodes commented
                Editing a comment
                What's the fun in that?!! ;-)

            • #9
              I already have epoxy, JB weld, Marinetex and who knows how many other candidates in my collection. Why buy something else? I know.... cheap cheap cheap.
              Atlantic City, NJ
              1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

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              • #10
                Well, here's the rest of the story. I didn't want to buy a new knob, because I had already gotten the knob with 3/8-24 thread, it's a really nice knob and, it was expensive.

                I tried repeatedly to make an adapter, but the difference between 8mm and 3/8 is just too small. There just wasn't enough wall thickness and when I tried to tap the I.D. it broke.

                So, I filled the knob with epoxy thickened with high density filler. I took an 8mm bolt coated with release agent and put it into the threaded opening on the knob. I let it harden and backed out the bolt. When screwing the knob onto the shift lever, the new thread actually behaved like a nut with a nylon insert and provided enough resistance when going on that it seems it won't loosen with use.

                Time will tell...

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