I.D. a carburetor

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  • November 19, 2017 at 1:27 pm #8692
    frankr
    Participant

      US Member

      I have this OMC carburetor. Without removing the throttle shaft, I don’t have a real good way of measuring the venturi, but it seems to be 1/2"
      My question: Is it a 5.5hp or a 7.5hp? I am thinking 5.5.

      November 19, 2017 at 6:16 pm #67629
      chris-p
      Participant

        Do you have any pictures to help? Casting numbers?

        November 19, 2017 at 8:26 pm #67636
        frankr
        Participant

          US Member

          Heh, I knew somebody would ask for a casting number. I was supposed to be getting ready to go to church when I was out messing with that thing. Anyhoo, I just looked again and found the casting number between the slow speed needle nut and the slot for the pull choke. As near as I can make it out it says 303, then below that, 045D. It isn’t very clear and hard to tell. And written upside down.

          January 18, 2018 at 2:42 am #69838
          Mumbles
          Participant

            Hey Frank, still trying to figure out what you have?

            I was building a 7.5 carb today and thought I’d compare it to a 5.5 and 3 horse carb. All three carb throats measure .900 – .915 at the choke end but that’s where the similarities end. At the butterfly valve end, the 7.5 measures .910, the 5.5 .750, and the three horse comes in at .625. In other words, 29/32nds, 3/4 and 5/8 of an inch. I couldn’t get in to measure the venturis.

            Also, a 5.5 carb will be drilled across the top in two places to pick up the throttle linkage shaft. The 7.5 carb isn’t drilled.

            January 18, 2018 at 12:38 pm #69849
            frankr
            Participant

              US Member

              Thanks mumbles. So with that info I went out and measured. It fits your description of 5.5hp. Then I beat a hasty retreat into the house. It froze here last night. Yeah, I know, you Canadians don’t want to hear our grumbling about being cold.

              January 18, 2018 at 6:17 pm #69863
              wbeaton
              Participant

                Canada Member - 2 Years
                quote FrankR:

                Thanks mumbles. So with that info I went out and measured. It fits your description of 5.5hp. Then I beat a hasty retreat into the house. It froze here last night. Yeah, I know, you Canadians don’t want to hear our grumbling about being cold.

                Grumble all you want, Frank. I think its harder for you folks that aren’t used to the cold. I once drove down to Texas in July. I thought I would melt into the pavement. I couldn’t get out of there fast enough. It was just a normal weekend to them.

                Wayne
                Upper Canada Chapter

                uccaomci.com

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