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Please help me with ideas for breaking airlock in intake water

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  • Please help me with ideas for breaking airlock in intake water

    I just got a new (to me) boat that's kept on a boat lift.

    When the boat is lowered into the water, the intake doesn't fill with water and as a result, the water pump is sucking air for quite a while before it finally starts sucking water.

    I'm thinking about putting a tee fitting in the intake hose and leading a hose off the tee to an easily accessible location where I could open a valve to let the air out before starting the motor.

    I'd appreciate any opinions on putting a tee in the intake hose as well as thoughts on a type of valve to use to ensure the it couldn't accidentally be left open such that the pump could end up sucking air. The ideal thing would be a valve that let air out, but not in.

    Lots of smart guys here, I'm hoping one of you has the great idea I'm after.

  • #2
    Odd...i don't have that problem on the lift. She starts sucking water real quick and if i remember the strainer is below waterline and fills on its own. Instead of bleeding the air could you close the seacock before lifting her up and then open it once in the water? I would not want to do that because I know i would forget to open it once in the water.

    Comment


    • wing15601
      wing15601 commented
      Editing a comment
      Hang the ignition key on the valve handle.

    • tcf25
      tcf25 commented
      Editing a comment
      Now that idea just uses too much common sense

  • #3
    Just add the flush setup on the other post and hang the key from the sea cock handle.
    1988 26' cuddy
    1975 20' open
    16' Sandpiper
    14' Certified Fiberglass

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    • #4
      You’ve hit on something. The boat in question is not a Shamrock and the strainer is above the waterline. Also, the intake hose is only 3/4”. To make matters even worse, the motor and the intake seacock aren’t easily accessible. (And I would probably also forget to open the seacock).

      Comment


      • #5
        How about a petcock at a high point that is accessible. Just bleed the air off
        '78 20ft Cuddy
        Mercruiser 350 FWC preVortec w/Carb

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        • #6
          Petcock is a great idea, but I need something that’s idiot proof. Or at least old man with CRS proof!

          Comment


          • #7
            Hang the key wherever the shutoff is.
            1988 26' cuddy
            1975 20' open
            16' Sandpiper
            14' Certified Fiberglass

            Comment


            • #8
              With the strainer above the waterline it will take a vacuum to fill it, either from the pump or some other creative source (tee with shop vac, etc.). Assume the strainer cannot be lowered.

              3/4" hose... What is this a sail boat with a small inboard?
              C Rhodes
              26' Mackinaw - 1990
              351 Indmar (1990-2006: Great Engine)
              351 PCM (2006 - Current)
              Southport, NC

              Comment


              • #9
                Originally posted by crhodes View Post
                With the strainer above the waterline it will take a vacuum to fill it, either from the pump or some other creative source (tee with shop vac, etc.). Assume the strainer cannot be lowered.

                3/4" hose... What is this a sail boat with a small inboard?
                Man, you guys are smart. Yes, it is a sailboat with a sail drive inboard.

                Comment


                • #10
                  In case anyone with a Shamrock has this issue (which I did on the 2008 5.7L Crusader with raw water cooling in the 1990 220 Predator I used to own), the previous owner had installed a hose fitting with an air bleed between the water pump and the 'octopus'. I think the fitting came from Mercruiser, as when I wanted find a spare screw cap, I found the replacement at West Marine was a Mercruiser part (blue wing-nut like-thing, only about 1" across, with a rubber O-ring seal). It always did the trick after a re-launch - I'd start the engine, open the cap, wait until the air was blown out and water started to spit. If I can find a photo of it I will post here. Warning: make sure to do this before the engine gets hot (which you want to do anyway to protect the engine from overheating) - otherwise you'll scald your hand when screwing the cap back in.

                  Comment


                  • #11
                    QuarterIrish, I'd love to see a picture of that setup.

                    A guy on my sailing forum suggested putting a tee in the intake hose and leading a hose to a point above the waterline and putting a plug in it with an 1/8" hole in the plug. He says the water will escape through that hole, but that the pump won't be able to suck air through it.

                    Comment


                    • #12
                      I think Quarter Irish is correct. The air bleed needs to be on the output side of the raw water pump, a bleed on the intake hose is akin to a hole in the side of a drinking straw. The bleed after the pump will allow it to lift the water and prime the pump without having to push the water though the riser.
                      Steve
                      1998 260 Mackinaw Sea Maxx 5.7 HO TBI 12' Klamath w/ 20hp Tohatsu EFI

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