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  • #1

    Carb strange problem

    Hi there!
    Need some technical advise.
    I use in my 29 feet sail boat a Yamaha F15 AMHS year 2004 - 2005
    outboard motor. After a total failure of its original carburetor I managed
    to buy and adapt a new carb used in 2006 and later F15īs. It performed very
    well, for about five years.
    After that it started to malfunction when in idle so I dismantled it, cleaned
    all openings I could get to with "ARBO Carburator Cleaner" spray and
    then flushed it with WD-40 spray (I donīt trust that ARBO Cleaner)
    I have the following situation now: The idle is still irregular and also
    the motor, after a few seconds, accelerate by itself, to about 2000 RPM
    then, after another few seconds falls back to the idle speed, then in
    a few seconds, starts this bahavior again and again. BY ITSELF!
    What the heck is this?
    Tags: carb malfunction, carb misterious behavior
  • #2
    Clean the carburettor properly (not with spray) and/or find the air leak.

    Comment

    • #3
      Plus 1 on re-cleaning the carb.

      Its revving up as its leaning out due to clogged jets, most likely the low speed.

      ALL the jets, high speed, low speed, nozzle, etc, HAVE TO COME OUT.

      The holes are extremely small and UN-LESS YOU CAN SEE LIGHT THRU THEM, that carb is NOT CLEAN

      Part #14 is the main jet, #7 the idle, #14 nozzle:
      http://www.boats.net/parts/search/Ya...TOR/parts.html

      Make sure a fuel pump is cleaned out of all crap as well or you get to do a third "do over".
      Last edited by TownsendsFJR1300; 09-02-2016, 05:38 AM.
      Scott
      1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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      • #4
        Thank you for your advise.
        What is the "Pilot Screw" (No. 2 on the drawing) for?

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        • #5
          pilot = idle /low speed

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          • #6
            +1 ^^^. Its for fine tuning the idle mix. As you can see, its under a cover, generally not messed with...
            Last edited by TownsendsFJR1300; 09-04-2016, 03:31 PM.
            Scott
            1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

            Comment

            • #7
              OK, thank you folks but ... just as a curiosity, how can the motor
              accelerate by itself then fall to the idle speed then accelerate again, all
              over and over without nobody touching it?
              Yes I checked the float and the needle, they are ok.

              Comment

              • #8
                Originally posted by kurylenko View Post
                just as a curiosity, how can the motor
                accelerate by itself then fall to the idle speed then accelerate again,                 all
                over and over without nobody touching it?
                Crap floating around the inside of the carb, clogging jets, leaning out(will raise the low speed when runnig out of gas).

                Did you physically check the jets?
                Scott
                1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

                Comment

                • #9
                  Timing changing will change RPM also
                  easy to monitor with a timing light

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