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2005 Yamaha 115 Won't Accelerate Above Idle Speed

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  • 2005 Yamaha 115 Won't Accelerate Above Idle Speed

    Yesterday I was returning from a fishing trip running at about 4,000 RPM on my 2005 Yahama 115 HP 4-stroke. Out of the blue the engine dropped to idle speed and from then on it won't accelerate in forward or reverse. Here are some details:

    1. I was in over 30 feet of water, and an inspection of the prop and skeg confirmed that nothing was hit.
    2. After removing the cowling I confirmed that the throttle cable is working properly. It moves as it should, but the engine doesn't respond.
    3. The engine idles perfectly and sounds fine. We made the last 45 minutes of the trip at idle speed with no issues.
    4. There were no audible alarms at any time.
    5. After letting the boat sit overnight to cool off I tried again this morning and the boat still won't accelerate above an idle.
    6. To be clear, the engine doesn't bog down or hesitate. It behaves as if I have not touched the binnacle throttle control. It just continues running perfectly at idle speed.

    Does anyone have any thoughts what might cause this?

    Thanks!

  • #2
    did you make sure the cable that was moving actually moved linkages to TPS and throttle plates?

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    • #3
      I did. We removed the cowl and I can watch the cable moving as is expected. This engine is EFI. Will it still have throttle plates?

      Thanks.

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      • #4
        Originally posted by Leew5408 View Post
        I did. We removed the cowl and I can watch the cable moving as is expected. This engine is EFI. Will it still have throttle plates?

        Thanks.
        Yes, pictured below and circled in blue are TWO throttle bodies connected by an adjustment (don't touch the adjustment).
        You have to have throttle plates to allow air into the engine. EFI, controls the fuel going in (via different inputs)

        When the throttle is opened/moved you should see those linkages/adjuster move as they ARE (should) move (open/close).

        Part #3 is the adjuster (again, don't touch but it should be moving when the throttle moves...




        Capture.JPG
        Last edited by TownsendsFJR1300; 10-26-2020, 03:51 PM.
        Scott
        1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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        • #5
          oops oops oops
          2000 Yamaha OX66 250HP SX250TXRY 61AX103847T
          1982 Grady Weekender/Offshore (removed stern drive & modded to be an OB)

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          • #6
            Scott,

            Thank you for the detailed response. I will take a look later this week.

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