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Outboard won't maintain prime

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  • Outboard won't maintain prime

    My 9.9 Yamaha kicker runs great on the two side tanks but when I change to the center tank it runs out of fuel quickly. I can squeeze the bulb til it get's hard and starts and runs fine til it uses the fuel in it's system.

    I replaced every fuel hose under the kicker cover, replaced the line fuel connector, replaced the fuel pump with the upgraded one and replaced the fuel line with squeeze bulb and connector to the kicker. All Yamaha parts.

    The hose is new that runs from the center tank to the fuel manifold.

    It has to be sucking air when on center tank. The 350 runs fine on all three tanks.

    OK, what say y'all???

  • #2
    Is the inside diameter of the center tank hose larger then the side tanks?
    1980 Glasply 2400 Cuddy I/O, 2017 Cummins 4BT
    1975 Glasply 19.5' Cuddy Merc 488 190 hp
    1997 Campion 525 Open Bow Ski Merc 125 hp outboard
    14' Inflatable sailboat
    16' Colman Fastback canoe


    • #3
      I think I finally figured it out! I am guessing the outboard was sucking air from the main engines carb. I just added a shutoff at the filter for the main engine. Seems to be working, fingers crossed!


      • #4
        Maybe it's not getting enough air from the main tank. When you run it from the attached (plug in) tank, it gets air from the filler cap valve.
        Glad it's working for you now.
        The cruise liner QE2 moves only six inches for each gallon of diesel fuel that it burns.

        1982 28' Long Cabin . SUP paddlers and kayakers transit the harbor with abandon, thinking they have the right of way over all boats.


        • #5
          Ran it for a couple hours today. I’d did die after 1.5 hours. I squeezed the bulb and it felt fine. Started right up so I don’t think it ran out of fuel. Other times in the past the bulb was soft after it died.

          Tank vent is fine as main engine has no issue running center tank. When I fill tank fuel shoots out of vent hole when full.


          • #6
            I'd put a check valve in your fuel lines to prevent sucking air in either line. I had a similar problem. Also stops the loss of fuel from back flow.


            • #7
              Check valve is another good idea.