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Beneteau ST44 A/C air block

Discussion in 'Technical Discussion' started by rbradbury, Oct 16, 2018.

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  1. rbradbury, Oct 16, 2018
    #1
    rbradbury

    rbradbury New Member

    Joined:
    Aug 6, 2017
    Messages:
    4
    My trawler is a 2014 ST 44 acquired last year in WI and now on the hard near Annapolis. Pretty much the only operational issue are the recurring air blocks that keep raw water from reaching the pump. With no water the heat or A/C is supposed to shut down, but usually does not. No water flowing causes the wet end of the pump to overheat and melt. My only solution so far has been to check the water each time it is turned on, and if no water is discharged, go to the engine room and remove the top of the strainer tube (sea cock closed) add a little water, then open sea cock and try again. This usually works but who wants to enter the engine room after 7 hours of cruising? The exterior clam shells are in place and forward facing, so that's not the issue. Anybody have any ideas? Thanks...
  2. Capt Ralph, Oct 16, 2018
    #2
    Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,741
    Location:
    Satsuma, FL
    We have worked over this many times on our boat and others.

    First think about this.
    Thrusters and clutching at the dock will insert air into the system.
    While running, the thru hull may pick up air as you pass over chop and your bow angle raises.
    Lifting strakes are A C killers if the thru hull is in the wrong position.

    A C pumps will not move air.
    The A C pump must be lower than the green water level out side your boat.

    The first thought of keeping your issue from happening, an uphill path to and beyond your pump. You want any air bubble to rise in the water column (hose) past the pump.
    As long as the pump has a water charge, it will pump.

    Grab a beer on a not so hot evening, crawl on down there, look over all the hoses. any hose from the sea cock that is not angled up to the pump needs to be re-worked.
    Grab another beer, is there any hose just above the pump discharge sloping back down forcing an air bubble to stay trapped in the pump.
    Grab another beer (for me it's a bourbon by now), think in the big picture, is there anywhere a hose droops down and back up below the pump or even close.

    Where is your ship located?
  3. Capt J, Oct 16, 2018
    #3
    Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,435
    Location:
    Fort Lauderdale
    Aside from what Capt Ralph has said, it can also be the hose between seacock/strainer/or pump is collapsing shut, or sucking air from somewhere. But usually it's the hoses being routed wrong with a constant uphill run to the pump. You should also call an a/c tech as the units should shut down on high pressure far before the pump melts the end.