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Marine head help!-gctid822662

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    Marine head help!-gctid822662

    Don't know if this qualifies as an emergency, but my wife would tell you it does.

    Among the systems I'm learning about bigger boats, I have never had to use a marine head. Thanks to youtube, I figured out how to flush it! But...when I do, I get a "bubble" that backs up into the head after 10 seconds or so. It's clearly coming straight from the tank because it will gas you out of the cabin. :sick: I'll pump out today, but is there something else that could be causing it?
    1999 Bayliner 3055
    2003 Triumph 150 CC
    2016 Yamaha VX Delux

    Check if the tank ventilation hose is clogged up, they have a nasty habit of getting clogged in the overboard connector
    1995 Bayliner 2452
    Alpha 1 Gen II
    2016 - 5.7 Vortec 4BBL
    Full Closed Cooling


      Assuming this is a manual head, pump to flush the choker valve at the base of the pump to water line may be bad allowing gas to back flow. However you holding tank may be overfilled, pumpout or clogged vent for the tank.
      1997 Silverton 362, 7.4 Crusaders
      1997 Maxum 2400 SCR, 5.7LX Bravo II



        Here is your test. Take the cover off the pump out deck fitting. Do the bubbles go away? Vent for sure.

        Be careful, as a pressurized holding tank can empty quite a bit through that fitting if it is close to full.
        Tally and Vicki
        "Wickus" Meridian 341
        MMSI 338014939


          Talman has an accurate warning that also is true pumping a tank that isn't vented well. Think about like this: you have pulled a vacuum on the tank that is suddenly released. Air rushes in, then there's the "fluid backlash".

          The Admiral is correct! If the proper appliance is there, it better be in working order.

          Agree that the vent is probably clogged and you probably need to change the joker valve. My approach would be to assume the vent is bad which is going to be problematic to pumping the tank. Not air out or in, right? Some vent air for pumping will come from the toilet but may be challenging. I would take a small screwdriver or awl to the screen or screen in the vent head and clear the holes. The screens are to prevent spiders from getting in and making nests and, at least mine, either clogged from salt or corrosion. The tank should "breath easier" now.

          Replace the vents, might as well do the potable water tank too, with stainless steel units. I'm not a fan of chrome plated zinc and the price difference isn't that much.

          Let us know how it goes.
          P/C Pete
          Edmonds Yacht Club (Commodore 1993)
          1988 3818 "GLAUBEN”
          Hino EH700 175 Onan MDKD Genset
          MMSI 367770440


            I've also had the plugged vent thing -- found that the tank had expanded and looked like a basketball!!! We were lucky it didn't burst.

            On mine, the vent is connected to a 90 degree PVC plastic threaded elbow that you'd commonly use in home plumbing. It was the elbow itself that had become clogged and the only way to tell is to physically remove it from the top of the tank.


              Just went thru this with a 38xx. Clear the vent tubing, and thru hull fitting. Also change the joker valve. If gas bubbles are coming into the bottom of the toilet then the joker valve is not closing like it should. Not a fun job, but a new joker valve will certainly improve the smell situation.

              Newport, Oregon
              South Beach Marina
              1986 3270 with twin 110 HP Hino diesels. Name of boat "Mr. Darcy"
              Past work history: Prototyping, tooling, and repair for Reinell,. General fiberglass boat repair starting in 1976.
              Also worked as heavy equipment mechanic, and machinery mechanic for over 30 years.


                Plastic drop cloths and disposable gloves are your friend here. You don't want the stuff that comes out of those hoses running all over! I had to do the joker valve when we bought our boat. Worst part was it wasn't even our discharge that was coming out of the line, it was the PO's. Gross either way, but the fact that is was someone else's made is seem worse.
                1993 Bayliner 3058 Cierra
                Twin 4.3L V6's
                Alpha 1 Gen II Drives
                Moored in Everett, WA


                  90 degree fitting on top of the tank.

                  Attached files


                    When I pump out I run a flush water hose directed at the vent fitting. The vacuum pulls the some water down the vent to clean it out a little bit. I do this pretty much every time and the vent has remained free flowing. Note that I removed the carbon vent filter two years ago with no adverse effects. I use Noflex digester chemicals. I have original waste hoses now 17 years old. They have a bit of an odor. The Noflex has helped but my wife tells me I need to change them.....
                    2000 4788 w Cummins 370's, underhulls, swim step hull extension
                    12' Rendova center console with 40HP Yamaha
                    MV Kia Orana
                    Currently Enjoying the PNW


                      Mix a teaspoon of Noflex in a spray bottle with water ( shake it hard Noflex is slow to dissolve in water)

                      spray on hoses and area around them. Just let dry do not wipe dry

                      If you can get to your hoses mix 2 oz Noflex with one quart warm water and wipe down the hoses with a cloth

                      If there are grains of product on the hose after no worry's just let dry.

                      You will be surprised on how well it works getting rid of the odors

                      Lot cheaper than replacing the hoses !