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Honda 9.9 Dies after 3-5 minutes at idle

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  • Honda 9.9 Dies after 3-5 minutes at idle

    I recently was given a small boat with an early 90's Honda 9.9 4-stroke with an electric starter. It hasnt been operated since 2002, The oil looked fine but I will change before going out. I was surprised that the motor started at all but it will start fine--has a good stream of water coming out of it, but it will die after 3-5 minutes running on idle. You can pump the bulb and it will run forever. I suspect a fuel pump is the problem. I took the fuel line off from the pump to the carb while it was running at idle and it is pumping fuel but I have no way of knowing if it is a weak stream or not I just know it was pumping.

    I had the tank valve open and even tried with the cap off. There was a small fuel leak where the fuel line connects to the motor but I fixed this by splicing the fuel line and removing this connector until I can get a replacement.

    There are two holes on the opposite side of the engine case from the water discharge opening--one looked like it was plugged with dirt from an insect--I cleaned it out with a small screw driver but I am not sure if it is open or not further up--could this be a air hose to the motor and could this cause the problem?

    The model number is BF9.9A and it had another number stamped in the motor frame I am assuming it is the serial #: BABS:1001490 can someone tell me the year of this motor?

  • #2
    Re: Honda 9.9 Dies after 3-5 minutes at idle

    There is an idle adjustment screw on the side of the carb, mayby open up a 1/4-1/2 turn and to see if that will help. There is also a drain screw there for the carb, maybe drain it and pump the primer bulb to see if you can clear any junk. Try mixing some Seafoam w/gas to help clean up the inside of the carb. There really isn't anything there other than the float/ needle vaIve , I did take the carb apart and clean it last year. I would think that a small amount of gas would keep it running, but I have never even looked for the fuel pump on my 15 (same engine) it just keeps runnig on.

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    • #3
      Re: Honda 9.9 Dies after 3-5 minutes at idle

      Make sure your idle isn't too low. The fuel pump needs adequate RPMs to pump. Make the task as easy as possible. The more fuel line it has, the harder it needs to work to pull it through. The further the fuel is below the powerhead, the harder it has to work to pull it up. Even the weight of the gas in the line affects pump efficiency. Larger diameter-heavier load. The line should be no larger than 8mm or 5/16in, I'd go for 6mm or 1/4" on anything under 20Hp. Make sure the tank vent is open and that it's not clogged.
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      • #4
        Re: Honda 9.9 Dies after 3-5 minutes at idle

        Thanks for the input--the fuel line does seem rather long--about 5' so I will shorten it and see if that makes a difference. I am thinking the fuel pump may be ok as it is pumping.

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        • #5
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          Re: Honda 9.9 Dies after 3-5 minutes at idle

          The problem turned out to be a potters wasp nest in the crank case hose. Cleaned the hose out and it ran like a champ.

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