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Yamaha 115 2 stroke has mystery engine cough

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  • Yamaha 115 2 stroke has mystery engine cough

    I have a 1999 Yamaha 115 2 stroke C115TXRX that has developed a “Cough” when it’s idling and continues when it’s in gear. It will idle fairly smoothly and about 20 seconds in it will miss and blow out a big exhaust ploom from the prop. It continues to do this until after about the 3-4 time it will kill the engine.
    A little history on this: about a year ago my inboard tank corroded through and I got a bunch of water and debris in the carbs. I had them ultrasonically cleaned and rebuilt. It ran fine when reinstalled but 2 weeks later when I went to put the boat in the water the motor would not start. After using a gas rag at the intake it started and that’s when the “Cough” started. The fuel is new, compression checked at 120 on cylinders, spark is good,timing is set correctly and I have had multiple people check it out. Does anyone have any idea what this could be? Also, can anyone tell me what the correct carb adjustment screws should be set to? (Last guy that checked it turned the screws but never set them back to the original position) Any help is greatly appreciated.

  • #2
    Sure sounds like it is a " lean sneeze "-----So partially block the carburetors one throat at a time to see which one might be the problem.----Report what you find.


    • #3
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      Agree with Racer...likely a minute piece of debris in idle circuit of one of the carbs...
      When in doubt,Trim it out!!!
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