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Loss of prime for water

Discussion in 'Big Boats' started by tadd5181, Sep 7, 2017. Add this thread to a FAQ

  1. tadd5181


    Joined Jun 6, 2004
    79 posts, 0 likes
    - -
    US San Diego
    My boat is a 2000 Hunter 420. I often lose prime ... causing inability to draw water (for sink, heads)...the pump runs endlessly. I have tried a solution that has worked in the past: open all water valves, including the stern outside shower, all to no avail. I have checked that my 3 water tanks have water levels at full or at least above half full. And repair agency suggested it is because the pump is "above water level"'s located under the starboard dining table seating and just forward of the nav table. The agency is suggesting relocating the pump below water (sea) level.

    It's hard to believe Hunter misplaced the water pump and the it needs to be moved. That would involve a great amount of re-piping.

    Any suggestions for regaining prime?

  2. Nodak7


    Joined Sep 28, 2008
    984 posts, 26 likes
    Hunter 41DS
    US Punta Gorda, FL
    Tadd, we have a Hunter 41DS and it does the same thing on the Port Water tank. It just happens at times. I looked at all the connections and have never found an issue. Whoever told you that the pump being "above water level" was the problem has no clue. Most water pumps draw there water from a tank and 90% of the time it is located above the tank. Anyway I will watch this thread and if if any of the suggestions apply to my similar issue.

  3. twalker H260

    twalker H260

    Joined Dec 2, 2003
    339 posts, 17 likes
    Hunter 260
    CA winnipeg, Manitoba
    I would be looking for an air leak between the tank and the pump - assuming your sure the pump itself isn't leaking.

    Likely above the waterline connections/line as you don't mention the water from the tanks being found in the bilge.

  4. Hardware


    Joined Jun 26, 2009
    5 posts, 1 likes
    Hunter 420
    US Olympia WA
    I have a 2001 420 and the only time I had that problem I took the sight glass off of the strainer between the manifold and the pump, cleaned the strainer, then put everything back together and it worked great. Other times it has been because of an empty tank. Switch tanks and no problems. Sorry I'm not much help.

  5. Terry Cox

    Terry Cox

    Joined Dec 25, 2000
    3,177 posts, 298 likes
    Hunter Passage 42
    US Shelter Bay, WA
    Hi Tadd, bizarro assessment, IMHO. Different boat and water system here, but our potable water pump is above both tanks and the only time we have had a prime problem is either a:

    1. Empty tank
    2. Clogged spigot at the tank.
    3. Clogged strainer that protects the pump.

  6. West Coast head ghost

    West Coast head ghost

    Joined Sep 9, 2017
    15 posts, 0 likes
    Catalina 30
    Ca Vancouver
    Hello try checking your tank vent line if it is clogged or plugged it will not allow the pump to draw water. Failing that.depending on the water pump type ,it could be a pressure switch or impeller problem. my guess is your tank that is plug

  7. West Coast head ghost

    West Coast head ghost

    Joined Sep 9, 2017
    15 posts, 0 likes
    Catalina 30
    Ca Vancouver
    Your tank vent is plugged. Every time a Boulder allows the water tank to flow through the air vent to know that it is full ,it is causing problems. even water sitting in the air vent hose can plug it.

  8. West Coast head ghost

    West Coast head ghost

    Joined Sep 9, 2017
    15 posts, 0 likes
    Catalina 30
    Ca Vancouver
    LOL not a boulder . was meant to say a boat owner.
    damn voice text .
    It's also possible that you have a shut-off valves in the tank line to pump which is been accidentally Beenclosed ,or there is a inline filter that is blocked.

  9. sea_casper


    Joined Jun 28, 2005
    426 posts, 6 likes
    Hunter H33 2004
    US Mumford Cove,CT & Block Island
    Had similar problem on 2004 H33, replaced pump, no problem.
    Replacement was about same cost as rebuild kits.
    Your pump is older.