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Sears Roebuck 1971 Throttle Issues

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  • Sears Roebuck 1971 Throttle Issues

    I recently acquired an old sears roebuck 5 hp outboard, which i believe to be a 1971 (definitely a 70s model). The engine runs, but when I start it, whether its at idle or full throttle it is constantly picking up and stopping. I'm not exactly sure how to describe it. It'll throttle, idle, throttle idle, like in burst of speed, and then eventually if it idles too long it will die out. Is this a fuel problem? I've recently cleaned the carburetor but who knows if I did it right. Thanks for responding!

  • #2
    Do you have the model # by chance?
    Every day is a new day..... GO FISHING and take the wife or she gets mad....

    1986 Durham 16 side counsel 35 Evin

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    • #3
      This is my first motor. Any clue as to where I could find the model number? Thanks for responding

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      • #4
        look on the transum bracket where it hooks onto the boat. The problem sounds like the fuel bladder. Do you have a picture of the motor you can post
        Every day is a new day..... GO FISHING and take the wife or she gets mad....

        1986 Durham 16 side counsel 35 Evin

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        • #5
          Here you go, the motor is in Jackson right now so I can't get to the model number.

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          • #6
            I'm still wondering if anyone has any clue as to what has been going on, I can email you a video of how the motor has been running, and I have discovered in my attempt to clean the carb I now have the bowl overflowing and leaking gas so that's another issue that needs to be fixed. Thanks for responding!

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            • #7
              I have zero experience with that model motor but, generally speaking, an overflowing bowl will cause the carb to flood the cylinders and I am surprised it does not quit running. Try to solve that problem first and see what happens. Good luck!
              Old geezer who never worked a day as a professional in the marine industry but has been fooling with outboard motors for 60+ years!

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              • #8
                That's a Tecumseh air-cooled 4-stroke engine almost exactly the same as a lawn mower engine.

                The float bowl overflowing and leaking are likely caused by a missing/damaged float needle valve gasket/seal (easy to lose when cleaning carb) and likely a damaged float bowl gasket (they get dried out).

                Your issue is called "hunting"...alternating low and high RPMs and is caused by too lean a fuel mixture.

                Adjust the idle mixture screw to 1 turn out from lightly seated and the main mixture screw 1-1/2 turns out from lightly seated.

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                • #9
                  Float or float needle& seat are causing the overflow. Fuel pump bladder is likely cause of the surging (IF it has one, since it is an on-board tank). If it does, are you aware that it needs to be installed in a certain rotational position?

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                  • #10
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                    Gravity-fed fuel delivery system on that one and no push-button primer either as it has a choke.

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