1972 Mercury thunderbolt 7.5hp carb

Home › Forum › Ask A Member › 1972 Mercury thunderbolt 7.5hp carb

Viewing 6 posts - 1 through 6 (of 6 total)
  • Author
    Posts
  • August 30, 2021 at 7:47 pm #245825
    vasrf1980
    Participant

      Hello,

      Looking for some advice on a 1972 Mercury thunderbolt 7.5hp the serial #3457860. The diagram on marine engine calls for carberator KB12A. I have looked locally, at the used outboard sites and ebay. I have not been able to locate one. The carb mounted on the motor is a KB54A and from my research is from a 30-35 hp motor. Yet it has a crack in the throttle body next to the idle mixture screw and is missing a few screws. I was thinking of trying to use some red loxk tight to seal it after i clean it and measure the jets to make sure they are the correct size. I have looked at the pre 70’s KB9A carbs and everything looks the same but the jets. Also will the newer WMB carbs work on tjis model. Sorry kinda hit a wall on this. Also if any one has an extra kb12A they wanna sell let me know. Thanks in advance

      August 31, 2021 at 5:30 am #245841
      billw
      Participant

        US Member

        Well that’s frustrating. I have two milk crates full of old Mercury/Tillotson carbs; but they are inaccessible until mid-September. They are in the basement of a house that I rent to a family for the summer. Mercury used a zillion different little ways of moving the throttle plate so I would be surprised if a WMB would just bolt on without any other changes…

        Long live American manufacturing!

        August 31, 2021 at 7:34 pm #245868
        vasrf1980
        Participant

          I appreciate the advice. It might come to me waiting and hoping your crates of wonders holds the magic carb. I’ve been calling around all day and checking to see if i could find one.

          Thanks

          September 1, 2021 at 11:57 am #245908
          vasrf1980
          Participant

            Well i found a guy with same year 9.8 with same style of carb. From my research the only difference between 9.8 Model M110 and 7.5 Model 75 is the jets in the carb. The 9.8 carb is a KB11A and the 7.5 is a kb12A. Looking at the power head diagran for both they have the same pistons and powerhead so should bolt right up.

            September 1, 2021 at 4:24 pm #245926
            billw
            Participant

              US Member

              The blocks are the same? Reed valves/center main bearing are the same?

              Long live American manufacturing!

              September 1, 2021 at 8:40 pm #245929
              vasrf1980
              Participant

                Yes sir, center main bearing/reeds, pistons and powerhead are the same part #

              • Author
                Posts
              Viewing 6 posts - 1 through 6 (of 6 total)
              • You must be logged in to reply to this topic.