Pumping head-low suction

Discussion in 'Sport Cruisers' started by TN Boatman, Oct 5, 2017.

  1. TN Boatman

    TN Boatman Member

    41
    Aug 31, 2017
    Maryville, TN
    1998 Sundancer SE
    7.4MPI B3
    question-my 98 270DA recently when pumping the head, suction on the hose is low and can hear air through the vent thus not sealed. Is there a one way valve that I am not aware of? This boat is new to me and every boat in the past was open access, connect hose to waste outlet and out it goes. Could be related to maserator and or switch? Am I missing something?

    Thanks in advance
     
  2. Korkie

    Korkie Member

    193
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags, Bravo III Drives
    If you have a vacuflush system there are 4, "duck bill" valves that dry out over time, do not seal properly and will need to be replaced. Test first by taking the hose off that comes from the toilet and plugging the inlet to the tank, if it will not create suction and stop running, then it is most likely the duck bil valves. You will need to take the pump assembly off the tank and dis assemble. Be sure to take a sharpie and mark the direction of each valve on the respective location. Just makes it easier to re assemble. I just had to do mine. Not a pleasant job. I took mine completely apart, motor and vacuum pressure switch off and pressure washed all of the pieces. Can get Duck bill valves on line, a bit pricey. Come in 2 packs. Put it all back together and you should be good for several years. Good Luck.
     
  3. TN Boatman

    TN Boatman Member

    41
    Aug 31, 2017
    Maryville, TN
    1998 Sundancer SE
    7.4MPI B3

    Korkie,
    I do have a vacuflush system. A quick google search and t pack valves for $21.00. Also read to flush LOTS of soapy water prior to starting project. Good thing to tackle next week. Thanks for the response!
     
  4. Korkie

    Korkie Member

    193
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags, Bravo III Drives
    It will require 2 packs - 4 valves total to do the repair.
     
  5. TN Boatman

    TN Boatman Member

    41
    Aug 31, 2017
    Maryville, TN
    1998 Sundancer SE
    7.4MPI B3
    I replaced valves (all 4) and was surprisingly easy and clean. Also replaced charcoal filter. Pumped out prior to winterizing and still hear suction through vent as if not sealing off system and creating suction. Never has this issue before and its like if I were to cover the vent thru hull port, is would work fine but should not have to do that. I feel like I'm overlooking that is very simple. Never had this issue before so think I'm going to check all connections and hoses next spring. No one will be using before then anyway.
     
  6. bahamabreisus

    bahamabreisus Well-Known Member

    Oct 25, 2007
    Hampstead NC
    500 dancer, previous 420,390,300 dancers
    detriot 8v92
    You should hear sucking at the vent. When using pump out there need to be air introduced back to the tank or it will not suck out. Duck bills have nothing to do with pump out.
     
  7. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Agree with above. Stuff out, air in. Similar to filling a gas tank - stuff in, air out. The amount of "stuff" remaining in the holding tank is your "seal". It's a dirt simple system. If it's not pumping properly, there may be a crack in the pump-out's dip tube. Or, maybe it's already empty - don't go by the "stain" on the inside wall.
     
  8. Sublimetime

    Sublimetime Member

    445
    Oct 22, 2007
    clifton nj
    420 da
    454
    my holding tanks have always had the pumpout connected to a fitting coming out of the bottom of the tank not diptubes.
    And as said above, If you are actually pumping out(meaning emptying the holding tank) you should be hearing suction at the vent fitting. If you hadn't heard it previously maybe it is partially clogged causing it to create a different pictch as the air is forcing thru.
     
  9. Blkbird

    Blkbird Active Member

    238
    Jul 5, 2010
    Lake Lanier, GA
    1997 Sea Ray 450 Sundancer
    Twin 3126 CATS
    Not to sidetrack the thread, but my head system makes a funny klunking noise when the system is on but the toilets aren't flushed. It does generates a vaccum, thank God, and when you flush the head it whooshes the crap away and the noise stops. Then the system regenerates a vacuum and the funny noise comes back.

    Symptoms of bad duckbills?
     
  10. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Kaklunka-kaklunka-kaklunka for about 30 seconds is the normal sound. Are you saying it has started sounding different than usual?
     
  11. Blkbird

    Blkbird Active Member

    238
    Jul 5, 2010
    Lake Lanier, GA
    1997 Sea Ray 450 Sundancer
    Twin 3126 CATS
    No it just keeps on making the kaklunka sound until I turn the breaker off. But there is a good vacuum.
     
  12. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Duckbills are good - you wouldn't make vacuum without them being good. Sounds like a pressure switch. Try this - flush the toilet, then push in a bit on the pressure switch after the pump has been pumping for 30 seconds to a minute. If that makes the sound go away, you've found the source. Now, if the microswitch has welded itself shut, it will never turn off. Or, the switch may not be making a good seal - you may be able to hear a hissing sound once you turn the pump off. You MAY be able to just clean it up (or replace o-rings if this is the cause), but if it's the original, it's due for replacement, anyways.
     
  13. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Let me back up a bit... Will the system HOLD pressure for at least an hour? Does water stay in the bowl?
     
  14. Blkbird

    Blkbird Active Member

    238
    Jul 5, 2010
    Lake Lanier, GA
    1997 Sea Ray 450 Sundancer
    Twin 3126 CATS
    Lazy,

    Yes, the water does stay in the bowl. Your thinking the seals around the ball might need to be replaced?

    Where is the pressure switch located? Do you have a photo?
     
  15. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Just trying to eliminate any other possible leak points, including ruling out duckbills. If you leave the toilet "primed" for at least an hour (ideally, it should stay for much longer) and still have your normal "whooosh", then that eliminates a bunch of stuff.

    No, I don't have a picture - but it will be located on your vacuum tank. It will have wires going to it, is a few inches tall and a couple inches across... has a spring mechanism.
     

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