1957 Evinrude 7.5hp Carburetor Questions

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  • June 19, 2024 at 1:04 pm #288404
    drifter
    Participant

      I was given a box of parts that once was a 1956/57 Evinrude (56 powerhead/57 exhaust housing) 7.5HP outboard. When finally completing the rebuilding the outboard I discovered that it ran very poorly. Diagnosis has led me to the carburetor. I discovered that the carburetor may be from a 1956 Evinrude 5.5HP and not a 56 Evinrude 7.5HP. The carburetors outwardly appear identical. However the bores – where the carb mates to the intake plate – are dimensionally different. One measures 23/32″ and one measures 13/16″. I have been told that the 13/16″ carb is for the 7.5HP powerhead. Can someone please verify?
      Also, the two carburetors share identical parts with the exception of the high speed nozzle. It appears the smaller carb (23/32″ bore on the 5.5HP) has a nozzle with 6 small holes and the larger carb (13/16″ bore for the 7.5HP) has a nozzle with only 2 holes. I’m told these nozzles can not be interchanged between carbs. Is this correct?
      Bottom line – The 7.5HP carburetor should have the 13/16″ bore with the 2 hole nozzle????
      Thank you for your help.
      Nick

      June 20, 2024 at 12:43 pm #288429
      fleetwin
      Participant

        US Member - 2 Years

        This is a good question, have often wondered the same thing.   So, I would imagine the larger bore, 13/16″ would be for the 7.5hp.  I wish I could give an answer about the nozzles, but would need a carb in front of me to figure that out.  In any event, interchanging nozzles would probably create a runability issue.

        June 20, 2024 at 1:49 pm #288432
        aquasonic
        Participant

          US Member

          I have a 1955 Fleetwin parts carburetor that I believe to be original. The bore measures 13/16″ and the nozzle has two holes.

          I don’t know about interchangeability of the nozzle between the 5.5 hp models and the 7.5 hp models, but I suspect there’s a reason for the difference.

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