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    Running Rich-gctid394640

    1994 Merc 5.7L, Carbed, Thunderbolt ignition. The last few months noticed more and more black smoke upon starting. Once the engine has been run for a few minutes, no smoke and have seen no noticeable change in performance.

    What are the proper steps to troubleshoot a rich running condition. Want to check things in a logical order without jumping around and randomly checking stuff.

    Already thoroughly cleaned the flamer arresstor.

    Full tune was done last season.

    Thanks.

    #2
    keithjabber wrote:


    What are the proper steps to troubleshoot a lean running condition. Want to check things in a logical order without jumping around and randomly checking stuff.
    http://"http://www.boats.net/parts/s...rding to this, you have the Rochester Q-jet carburetor.

    Your thread title says; Running Rich, but you are asking about a lean condition.

    The only external adjustments that can be made pertain to the low speed metering circuits.

    These will be the air screws.

    Turning these screws IN reduces air, and fattens up the low speed metering.

    Turning these screws OUT increases air, leaning out the low speed metering.

    In order to make any adjustments that will affect high speed metering......, you'll need to get into the carburetor.

    .
    Rick E. Gresham, Oregon
    2850 Bounty Sedan Flybridge model
    Twin 280 HP 5.7's w/ Closed Cooling
    Volvo Penta DuoProp Drives
    Kohler 4 CZ Gen Set

    Comment


      #3
      OK, let's take a step back to make sure I define the correct condition.

      What are the indications of running rich? Lean?

      Comment


        #4
        keithjabber wrote:
        OK, let's take a step back to make sure I define the correct condition.

        What are the indications of running rich? Lean?
        Rich typically implies more fuel than air with regard to the correct fuel/air ratio.

        Lean would be just the oposite of this.

        Rich may be indicated by the black exhaust smoke that you describe.

        Lean conditions seldom reveal any visual charateristics via exhaust gasses.

        Spark plug readings can be usefull, but we must check imediately upon shut down, and upon after having run at the suspected RPM and Load.

        Otherwise, we loose the readings.

        .
        Rick E. Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
        Kohler 4 CZ Gen Set

        Comment


          #5
          You may want to check your choke operation before adjusting air mixtures. It was always my choke when it started up black and then smoothed out when it warmed up.

          Comment


            #6
            2850Bounty wrote:
            http://"http://www.boats.net/parts/s...rding to this, you have the Rochester Q-jet carburetor.

            Your thread title says; Running Rich, but you are asking about a lean condition.

            The only external adjustments that can be made pertain to the low speed metering circuits.

            These will be the air screws.

            Turning these screws IN reduces air, and fattens up the low speed metering.

            Turning these screws OUT increases air, leaning out the low speed metering.

            In order to make any adjustments that will affect high speed metering......, you'll need to get into the carburetor.

            .
            Now I see my typo and the start of the confusion, that's fixed now, Thanks.

            Comment

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