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  • Fuel Tank Replacement Questions

    Wow... this board is a great resource. This is my first post here, sorry if I get a little long winded.. I'm the 3rd generation owner of our families 1975 17' Mako CC. I'm replacing the internal gas tank. The old tank is out, the new one (aluminum/w epoxy coating) is on the way. I've cleaned out all the gas soaked foam, gave the walls of the 'coffin' a light sanding and wiped it clean with Acetone. For those of you who have done this, at the bottom of the coffin are 4 holes i guess for drainage. My first question is, should I seal these holes with something..maybe plastic covers and some 5200? Or leave them open and just let the foam fill them in? My second question..From what I've read, others have used 4lb foam... I wish i found this site before I ordered my foam, but I got 2 lb foam. Will this be sufficient? If you are familiar with the coffin layout, the gas tank will be supported in the corners and up the middle by built-in platforms. Should I put any material between the platforms and the gas tank? Neopreme or similar? The old tank looked to be just setting on them encased in foam.

    The aluminum fill and vent tubes look to be in decent shape, however they do have some pitting on them. Has anyone had any success with getting them out and replacing them with some USCG approved flexible lines? Any tricks for this process?

    I'll end my questions for now.. I appreciate any responses and will keep you all informed on my progress.

    Thanks again.

    C
    1975 Mako 17 w/2005 Yammy 90HP, Annapolis, MD

  • #2
    Sounds like you have the project under control. I replaced the 160-gal tank in my 231 two years ago. It's a stinky job...carving out all the foam and letting what remains under the coffin dry out. I assume you have given it ample time to let any fuel residue left in the foam under the coffin evaporate. It took about 10 days for the smell to go away in mine.

    Mako used to place rubber or neoprene spacers between the tank and the platforms it rests on. These are more to prevent chafing than anything, but they are important. I used some rubber adhesive to hold them in place until the tank was lowered on them. On the monster size tank in the '89 231 there were bolt assemblies for anchoring it in place on top of the tank so there would be no movement. 160 gal of fuel is a lot of weight an you don't want any shifting.

    I foamed my tank right to the top on all four sides so the foam acts as side support and a buffer between the tank edges and the coffin sides. That was the way it was installed originally. I don't believe the tank is very large in the 17 so don't go apoplectic about using 2-lb. foam. Shouldn't be a factor.

    My boat had rubber fill and vent tubes, not aluminum, so I can't help there.

    Good luck,

    C-Fish
    [br]Mako To Go, Brick, NJ [br]1989 Mako 231 CC[br]250 Optimax[br]

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    • #3
      Channel Surfer,

      One last thing. Do not seal the holes in the bottom of the coffin. If you can, dig out as much of the foam as you can through the holes that have been fuel soaked and aim a fan or hair drier down there to aid fuel evaporation. The new foam will flow down into the holes and adhere to the old when you foam in the new tank.
      [br]Mako To Go, Brick, NJ [br]1989 Mako 231 CC[br]250 Optimax[br]

      Comment


      • #4
        C-Fish,

        Thank you for your suggestions on the foam and the neopreme. The boat has been airing out for 2 weeks now in preparation for the tank. I will need to dig down in those access holes again to make sure all the old foam is completely out. Any technique to applying the new foam? The stuff I bought gets mixed then you have about 30 seconds before it goes off. I'm guessing since I have the center support for the tank, just pour equal amounts on each side of of the tanks then just put some weight on it till it expands? Or should I do small amounts under the tank first then put the tank in and do the sides? Never used the foam before, looking forward to it.

        Thanks for replying,

        C
        1975 Mako 17 w/2005 Yammy 90HP, Annapolis, MD

        Comment


        • #5
          The foam kicks off very fast once you mix the catalyst and it is very difficult to guestimate how much you are going to need in one shot. I did what was recommended by a fiberglass guy I know. I bought a half-dozen paper paint pails, they hold about a gallon each and are available at any paint supply house, and mixed up small batches. Each batch was mixed throughly using a paint mixer attachment and electric drill. The mixer is just a long, metal rod with a little plastic prop on the end. Then I began by pooring it under the tank first and allowing each batch to expand until it was done. Then I'd mix another and pour around the first. By the time you get near the top of the tank you have a pretty good idea how much it will take to fill the remaining void spaces and won't over do it. You also don't end up having the stuff go crazy catalysing while your trying to poor it.
          [br]Mako To Go, Brick, NJ [br]1989 Mako 231 CC[br]250 Optimax[br]

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          • #6
            I did the same thing to my '73 22 CC about 3 years ago and have a couple of suggestions for you. First if you have the tank out and can replace that aluminum fill pipe do it as it will only start another problem in a few years. By now you know that to get to it there is alot of work involved. Use the USGC approved 1 1/2 inch fill hose and the coast guard 5/8 in tank vent hoise to replace what is there now. My boat's fuel tank was in good shape when I pulled it out (probably would have lasted at least another 5 to 8 years) but did find my gas leak which was the AL fill pipe from the gunnel. The my foam around the tank was also in not wet or gas soaked so my tinking was that if it had lasted almost 25 years I would redue it the same to last another 25 years. The four holes in the coffin were used by Mako to get some foam into the builge under the tank for some support for the coffin and inbetween the stringers. When I had my tank out I dug out as much of the foam as I could reach in each hole, dried it out real well and then filled each hole with foam. I let it foam up into the coffin until it was level with the foam pad that my tank sat on. You may need to cut a little off here but it will fill the viods completely providing a flat surface for the tank to rest on and ashould seal out any water that gets into your buldg. My tank was held down in place by 2 - 1 inch aluminum angles that were bent on each end so they could be screwed into the sides of the coffin. Each one was placed about 1/4 of the way from the front and rear of the tank. When I redid these angles, I made up 2 heavy duty ones with welded brackets on each side where the screws went into the coffin. I also spent some time and reinforced the areas of the coffen where these screws went into the sides of the coffin. The only thing I used between the angles and the tank was a bead of 5200 to prevent the tank from actually touchning the angle without some sort of isolation. Also remember to place your grounding wires on the tank and the gas fill so you don't end up with a spark when ypu put the gas fill nozzel into the boats gas fill.

            Hope this helps

            Mike
            1973 22 CC Milford, CT USA[br]

            Comment


            • #7
              Mike,

              Thank you for your suggestions as well. The tank should be here Monday and I can't wait to get that thing in there. I will post my progess. I appreciate your feedback on the fuel feed, ground wires, and safety brackets.

              Thanks again,

              C
              1975 Mako 17 w/2005 Yammy 90HP, Annapolis, MD

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