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Power Issues Post-Carb Clean

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  • Power Issues Post-Carb Clean

    1998 S115TLRW


    Past few times out was experiencing a stumble upon 1st throttle up leaving boat ramp. After that slight stumble, no issues. Coincidently, this came right about the time carbs were due for PM. Pulled carbs and jets, installed new kits, checked floats, and reinstalled. Time and synced. Starts and idles good. No power when throttle up. Deep throaty sound. Enough power to get on plane, but running at half speed.

    Installed new fuel pump and fuel filter cause they were about due. Pulled carbs and jets again...verified each of the 6 jets were clean and clear enough to see through when holding up to light. Checked floats and reinstalled. Time and synced. Starts and idles good. Same issue...no power when throttle up.

    Same fuel in the tank as when there was only the slight stumble. No hint at water in fuel. Primer bulb is full when experiencing the power issue.

    Other than dumping fuel, which I don't believe is the issue, I've troubleshooted the entire fuel system. Any thoughts...did I miss something? Gonna move on to spark next.
    Jason
    1998 S115TLRW + 1976 Aquasport 170

  • #2
    You posted verifying 6 jets open. There should be 6 main jets as well as idle jets. Were ALL jets pulled and checked?
    Jets 9 &12: https://www.boats.net/catalog/yamaha...lrw/carburetor

    Your issue sounds very much like a fuel delivery issue.

    If you can get a get a helper, to verify it is a fuel issue, I'd try the following:
    When the engine is bogging (cowl off-underway), spray some pre-mix (from a hand held plastic spray bottle) into the air intake.

    The engine (if a fuel issue), should jump to life and take off momentarily.

    That'll narrow down the issue at least..


    Lastly, can you gently sneak up on the throttle and get the RPMs up (underway)?
    Last edited by TownsendsFJR1300; 08-24-2019, 07:52 AM.
    Scott
    1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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    • #3
      9s, 12s, 14s were pulled and verified clear. I have enough power to get on plane, slowly. Top out at 4k. Should be mid 5k.
      Jason
      1998 S115TLRW + 1976 Aquasport 170

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      • #4
        did you verify that the timing is advancing as it should?
        have you verified all plugs have spark when problem shows up?

        checking when the problem is not there does not tell you much.

        running off of a portable tank with fresh gas would tell if the gas in your main tank is a problem

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        • #5
          Haven’t moved on to spark just yet...was r/o fuel 1st. But definitely no biggie to check/replace plugs. I have not looked. Timing looks good. Throttle valves open/close appropriately.

          Re: portable tank...indeed it wud. Last resort only cause same fuel in tank now as when not having these issues.
          Jason
          1998 S115TLRW + 1976 Aquasport 170

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          • #6
            so tell us what is the timing sitting at when the motor is having trouble/bogging.

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            • #7
              Originally posted by 99yam40 View Post
              so tell us what is the timing sitting at when the motor is having trouble/bogging.
              Gonna be at the boat this eve. Will do, thanks.
              Jason
              1998 S115TLRW + 1976 Aquasport 170

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              • #8
                Did you clean all the passages in the carb itself, not just the jets?

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