7.5hp Cranks OMC (Edited Journal Clearances)

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  • September 30, 2015 at 11:48 pm #24944
    chris-p
    Participant

      All my rods are a bust.

      After polishing out the flaws, they measure about 0.8111 to 0.8115

      The spec in the manual is 0.8120 to 0.8125

      Too bad, cause they look shiny! 😉

      In fact, the best measurement I could get on any of them was 0.8120. But that was only on 1 of the 4 journals.

      Anyone have a good crank they can measure? Im curious if 0.8120 was factory. What is normal wear after this many years?

      October 1, 2015 at 1:38 am #24953
      dan-in-tn
      Participant

        US Member

        Chris; I don’t know what age you are, but I have been wondering for awhile now about an idea on these bushing rods. I would appreciate any feedback from anyone on the idea. Worked on cars, but they have oil pressure bearings. Ford used a conn rod bearing that spun inside the rod and on the crank pin also up to about 1948 on the flathead motor. Had a mechanic tell me once that he would have starved to death if he had to make a living grinding those cranks. They never needed grinding since the wear was cut in half.Wonder if we could gain enough thickness for such a bearing from the rod and crank? Would it get enough lube to the bearing at high speed? Just trying to dream up a way to save these old cranks and rods!
        I have put 6hp cranks in 5.5hp with needle bearings and that works great, but don’t have a motor that has a crank close enough to steal the parts for the 7.5hp that I have found.
        Still thinking!

        Dan in TN

        October 3, 2015 at 8:28 pm #25064
        garry-in-michigan
        Participant

          Lifetime Member

          Some ware can be compensated for by taking material off the rod and rod cap and then reaming it out undersized. You could also try tinning the bronze bushing with lead free solder. It is made with tin and silver and polishes to a very slick surface.

          About ten years ago I was curious about the approximate cost of building titanium connecting rods for a small two cycle motor. (2.125" bore by 1.75" stroke). As I recall, the first connecting rod was $3000, but the rest were only $1000 a peace. These of course had needle bearings on both ends. . . . 😀

          October 3, 2015 at 10:15 pm #25071
          chris-p
          Participant

            I have some cranks that are shot, so maybe Ill be a guinnea pig!

            I am envisioning your idea here Dan. If the rod and cap are bored out, to allow for a 2 piece, floating "shim" perhaps? Im not sure if there is enough meat there for actual needles? Maybe if you take meat off the rod/cap, and some meat off the actual crank as well, you could add in needles?

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