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38xx Fresh Water Tank Replacement - Has anyone done a bladder in original place?-gctid802312

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    38xx Fresh Water Tank Replacement - Has anyone done a bladder in original place?-gctid802312

    Have been spending some time searching, found a few good threads, but have not found one that suggests someone actually has done a replacement with a bladder in the original location.

    I am leaning towards this type of replacement because its less money, more likely to get closer to (or greater than ) original capacity, and I am happy using an access hatch / visual in lieu of a level gauge.

    Main questions are :

    1) What size to get

    2) What does the filler fitting actually look like/what type of threads?

    3) Is building a "box" to contain the bladder shape or other abrasion or movement prevention necessary?

    If your bow is light and can balance the boat with more weight FWD, then move the tank to under the FWD berth, and then you can buy a less expensive solid tank for that location.

    Bayliner 3870 "ALASKA33)
    Twin 350 GM power
    Located in Seward, AK
    Retired marine surveyor


      I carry 167 gallons of water.

      I installed an additional 40 gal bladder fwd of the holding tank.(It has a separate fill left of the windlass switches) and I ran a line with a shutoff and T into the main feed line in the galley.

      I also installed a plastic 47 gallon tank in the locker at the foot of the guest stateroom (I accessed behind the fridge) I cut into the main fill line and ran it to the 47 gallon tank so the 80 gallon tank fills thru it and then it fills when the 80 gallons is full. It has it's own sending unit, the bladder does not.


        I researched bladders. It is my understanding that the tank has 2 bulkhead inside making it a 3 section tank. I have a leak as well but like others don't relish the rip and tear aspect of demo and replace with less. I haven't done this yet but will update next month when I do.

        I am in the water business and deal with tanks frequently so I going to patch and seal. The plan is to cut the floor out full length of the tank, exposing approximately 16" wide by 72" long give or take. It's my understanding that this is a double thick floor in most of the area. The idea is to leave a flange on the lower floor to support a hatch/ replacement for the upper floor.

        With the tank exposed I will cut an access hole 10"x10" in each compartment, should be 3. This will allow access to the entire tank from the top. I should be able to throughly clean the tank through these holes.

        Garco LM60 is what I will be using for the sealing. It requires a primer to work for aluminum but should be easy to apply with roller and brush to the entire inside of the tank. LM60 is approved NSF61 for use with potable Water and has a recommended 50 year life.

        After sealing the tank I will cover each hole with a 1/8" plate screwed down and sealed with 5200. I'll let you know how it goes. Cost of the sealer and primer was $500 bucks. The smallest size container for sealer was 5 gallons and primer was 2 gallons. Both are 2 part mixes. I can't imagine using more than a gallon of each. If I have a bunch left over I will let you all know and woul be willing to share to to help bring the cost down.


          Dave, before you do the patch, take a look inside of your water tank. When I was resealing my sending unit and looked into the tank and saw all sorts of stalactites, giving me nightmares about how soon my tank will start leaking. If I were to try to salvage the tank, I'd cut the bottom out and replace the sheet metal.
          P/C Pete
          Edmonds Yacht Club (Commodore 1993)
          1988 3818 "GLAUBEN”
          Hino EH700 175 Onan MDKD Genset
          MMSI 367770440


            Replacing my water tank was my winter project this year. Bayliner literally built the boat around the tank. It is quite a job. There are a couple of threads on BOC on the replacement and I read them numerous times as I did my work. To extract the tank and install a bladder may not be a bad idea. It's the tear out that is a bugger. I didn't get as intrusive with my extraction as one of the threads suggests. Our boat's PO installed an additional water tank under the master berth which is a big additionfor my family.

            Still putting the last screws back into the completion so the project is pretty fresh in my mind if you have any questions.

            1988 38'
            Shear Bliss


              Cory - thanks - yes, wondering if you were able to do it without tearing into mid stateroom and also what tank(s) did you swap back in?


                Dave - had not considered that approach - sounds promising - Would that approach depend on likelihood of other future leaks plus I think the unknown of if you can actually reach where its leaking to patch without more demo?

                Wanna split the sealer ??



                  Sent you a PM. No tearing out of the mid stateroom.
                  1988 38'
                  Shear Bliss


                    Absolutely. With an 10" access hole in each section, it should all be reachable. This sealant is brushable, trowlable so is pretty thick and should be easy to coat everything, even the top surfaces. I'll split this stuff up in to gallon quantities this week. I'm planning on making the section of sole I cut somewhat hatch like so I can get back to the 3 inspection holes in the future. With the entire tank only 36" wide everything should be accessible from the holes.


                      Did you document any of your project Cory with pictures? Thanks


                        Thanks dave - let me know how it looks. I think what I'll do is go ahead with pulling up the floor and cutting some holes, at least enough for a boroscope if not a flashlight. If the bottom looks good except the one leak I may pursue a patch.