Throttle stall

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  • genefa
    Frequent Contributor
    • Jun 2006
    • 7

    Throttle stall

    I know there is some relationship between accelerating by moving the throttle and response of the engine, but I have forgotten it. Recently I adjusted the screw on the carburetor b/c my spark plugs were showing some carbon on them. After adjusting, while tied to the dock I accelerated the throttle and the engine coughed and almost stopped had I not decreased the throttle. Could someone remind me of what I may need to do to allow the engine to respond to a quick increase in throttle? Thank you. Amigo.
  • sastanley
    Afourian MVP
    • Sep 2008
    • 7035

    The adjustment screw is for idle fuel/air may have created too rich a mixture and as you increase throttle the relationship between the idle jets and the main jet in the carb is not kosher.

    The 'adjustment' screw is for fuel/air mixture and base setting is 1.5 turns out from all the way in. When at the base setting and the engine at idle, you can adjust the screw to get the best running engine at idle. It is usually 1/2 turn or so in either direction.

    Then, as you increase throttle to about 1,200 RPM, the main jet should take over.

    That's all I know about the relationship between the throttle & engine response. I sometimes get a little lag/stumble when I give the engine throttle too quickly..I try to give her gradual throttle when I can to keep her happy.
    "Holiday" - '89 Alura 35 #109
    "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!)


    • smosher
      Afourian MVP
      • Jun 2006
      • 489

      If the engine stumbles from idle to power the idle mix is too rich, which will
      also make your plugs black with Carbon. This is an air bleed carb so adjusting the screw clockwise will richen up the mix, opposite of what you may think. To lean it out turn counterclockwise.

      Mine is set to 1 1/2 turns, which is where Don recommends as a starting point.



      • roadnsky
        Afourian MVP
        • Dec 2008
        • 3129

        Bear in mind kids that the idle setting is a little different IF you have the PCV valve (crankcase ventilation) installed.

        'Lone Ranger'
        1978 RANGER 30