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Thread: Fuel tank leaking. Will replace.

  1. #1
    Join Date
    Oct 2018
    Location
    Saint Petersburg, FL
    Posts
    12

    Default Fuel tank leaking. Will replace.

    The 35 gallon diesel tank in the port hull of Cyclops has begun leaking. It's leaking enough to saturate 1/4 of a Pig diesel absorbent pad every two days. I marked the tank's sight glass, and it's taken about a week for me to be 100% sure that the leak is from the tank itself. The leak must be from a location I can't see, and there isn't corrosion or a crack where I can see.

    Has anyone replaced their fuel tank yet? Cyclops is a 1991 P35. I replaced the engine in the port hull 2-3 years ago, and now I'll need to pull that engine back out, so I can have access to the fuel tank area. I *think* that I might be able to extract the tank through the aft cabin, if I cut a hole large enough to slant the tank as I lift it up. I'd really like to avoid having to also cut access through the "sun pad"/roof of the aft cabin, and mess up the anti-skid texture there.

    I think I'll have a custom aluminum tank made, and mount it differently than the current tank, so that its exterior will remain dry. The current tank's base gets occasionally wet with bilge water, and I'm guessing that's where the leak is.

    I'm not going to immediately replace the tank, just drain it. I've got a bunch of other projects underway, so if I need to fire up that engine in the meantime, I'll install a temporary smaller tank. Maybe even run fuel lines to the other hull too, so I can turn my portable fuel polishing gear into a permanent setup for both tanks, and also be able to pump fuel between the tanks.

    When I do replace the leaking tank, I'll be sure to post some pictures and commentary here. Maybe I'll post a YouTube video too.

  2. #2
    Join Date
    Oct 2018
    Location
    Saint Petersburg, FL
    Posts
    12

    Default Re: Fuel tank leaking. Will replace.

    Just realized I had a typo above. Cyclops is a Privilege 39, not a 35 (which I don't think exists).

    So, nobody else has yet replaced a tank on one of the early generation boats?

  3. #3
    Join Date
    Apr 2011
    Location
    New Jersey and Cruising
    Posts
    29

    Default Re: Fuel tank leaking. Will replace.


  4. #4
    Join Date
    Oct 2018
    Location
    Saint Petersburg, FL
    Posts
    12

    Default Re: Fuel tank leaking. Will replace.

    Very nice blog you have! Nice pictures of the work, too.

    When I bought Cyclops, about 3 years ago, its original water tanks were already out of service. They were located in the forward storage compartment, unlike your placement in the amidships bilge. As an aside, my amidships bilge is quite deep, and shaped quite differently than yours.

    The original stainless steel tanks were too large to be extracted through the hatch, so a previous owner placed a 40 gallon cylindrical polyethylene tank atop each of the original tanks. They cut an opening in the front of each of the stainless tanks and stored random items inside. Not long after I took ownership, a very strong chemical smell came from the port hull storage compartment. I found a corroded metal container of polyester resin hidden away in the back of the old stainless tank. It had leaked about a gallon of resin into the tank, which contained it, but the smell was untenable.

    It was time to remove the stainless tank, and I'd need to cut it into pieces first. With flammable resin present, I couldn't use an angle grinder with a cutting wheel. The sparks would surely have ignited it. The stainless was pretty thick, and very quickly dulled Sawzall blades. I ended up buying a Fein 6 gauge sheet metal nibbler ($1250, used condition) which worked very well. Once the top was off, I could see that the resin had spread through the tank baffles and coated the entire floor of the tank. I stirred some catalyst into the resin and metal shavings. That was reasonably successful in stabilizing the resin, with only a little of it remaining unhardened. I didn't want any of it dripping onto me when I would eventually have to lift it overhead and through the hatch.

    It took a while, but I eventually cut the tank into pieces small enough to fit through the hatch, and brought it to a local recycler. They didn't care about the hardened resin on the metal. I re-mounted the cylindrical tank, now sitting on the hull. I've yet to remove the water tank from the starboard hull, but that is planned for the future. It'll be somewhat easier to do, since I won't have to wear a respirator.

  5. #5
    Join Date
    Oct 2018
    Location
    Saint Petersburg, FL
    Posts
    12

    Default Re: Fuel tank leaking. Will replace.

    I pumped the tank empty today, and found that (surprise!) it's not a 35 gallon tank. It's sight glass has some gallon number-lines scribbled nearby on the tank face. The numbers are every 5 gallons, from 5 to 30, such that a full tank would be 35 gallons.

    Well, according to the sight glass, I started with 20 gallons indicated in the tank. I ended with 37.5 gallons in jugs. Previously, when I've re-fueled, I've never been below 15 gallons indicated, and I stop filling it at the 30 gallon mark. That range has always accurately matched the fuel pump's gallon meter, so I've never had any reason to doubt that the sight glass labels were incorrect. It turned out that there was a whole lot of fuel remaining below the 5-gallon mark.

    So, maybe the tank size is actually 52.5 gallons. The tank is quite likely original to the boat, because the tank's manufacturer label is in French. The label says the tank capacity is 242 liters (63.9 gallons), which seems unlikely but possible. :-) I found the label near the fuel level sender, which I removed in order to insert the intake probe of my fuel polisher, to drain the tank.

  6. #6
    Join Date
    Aug 2009
    Location
    Stratford upon Avon
    Posts
    3,417

    Default Re: Fuel tank leaking. Will replace.

    This one heck of an exercise. Have you started on the starboard tank yet?

    Cheers!

    Mike
    Nothing works on an old boat, except the skipper.

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