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Fluctuating throttle and no reverse

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  • Fluctuating throttle and no reverse

    87 Yamaha 115. Ran it around the other day and at about 3/4 throttle it fluctuated every few seconds, dropping rpm slightly then coming back up without me touching anything. Then as I headed back to the ramp, reverse would not engage at all. It would rev and grind, but never kick in, even after trying to drop in into reverse with some authority.

    Got it home, pulled the cowling and see this. Both adjustment screws were loose, just hanging out not remotely close to being tight. Im hoping this is the cause of the throttle and reverse issues, but I dont know how to adjust accurately. Any ideas on general adjustments that would at least get me to a starting point??




    Tampa, FL[br]\'81 Mako 17 Standard w/ \'87 Yamaha 115

  • #2
    Same thing happened to me on my Johnson.

    I would play with those adjustments by turning them in the same direction that would engage reverse.

    With the motor and batteries off try to turn the prop in the reverse direction with the shifter in reverse of course.

    You can tell whenreverse engages and disengages by whether the prop spins or not.

    Once you are certain that reverse does engage make sure neutral and forward are also correct

    You might have to do this more than once if it keep skipping while on the water.
    1971 Angler 17[br]2000 Johnson 150[br]Miami, Fl

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    • #3
      quote:


      Originally posted by ralph50


      Same thing happened to me on my Johnson.


      I would play with those adjustments by turning them in the same direction that would engage reverse.

      With the motor and batteries off try to turn the prop in the reverse direction with the shifter in reverse of course.

      You can tell whenreverse engages and disengages by whether the prop spins or not.

      Once you are certain that reverse does engage make sure neutral and forward are also correct

      You might have to do this more than once if it keep skipping while on the water.


      Thanks ralph50, Ill start there and see what happens!
      Tampa, FL[br]\'81 Mako 17 Standard w/ \'87 Yamaha 115

      Comment


      • #4
        I am not so sure that the up and down revs are related to a loose screw. That symptom is often due to a clogged/dirty VST filter or a clogged fuel filter.
        Your best bet for adjusting the cables is getting a service manual but in a pinch this method will work:
        Undo the shift cable. Manually move the shift rod onto reverse. You should rotate the prop by hand while shifting.
        Now move the shift control at the helm into full reverse (it is still not connected at the motor. Connect the end of the cable to the shift rod and adjust the cable so that it fits into the clamp or pin. Now mark the cable rod with a sharpie where it goes into the sheath.
        Disconnect the cable again and now manually shift the motor into full forward. Shift the helm control full forward and now reinstall the cable at the motor. If the cable clamp/pin fits mark the cable rod where it meets the sheath. If it doesn't fit, adjust the cable length until it does and then mark the cable.. Disconnect the cable again and move the cable in and out. You will have two marks. Make a third mark in the center of the two marks. Now with the motor shift lever in neutral and the control at the helm in center/neutral reconnect the cable at the motor. Adjust the cable as needed to get that center point mark at the end of the sheath.
        That should do it.

        The throttle adjustment is simpler. When the control lever at the helm in in neutral adjust if needed the cable clamp/barrel adjuster until the end od the cable fits onto the throttle lever with the throttles closed (the idle adjuster touching the stop)

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