Plastic Fuel Tank Questions

Discussion in 'Fiberglass and Composite Boat Building' started by glastronjohn, Nov 10, 2009.

  1. glastronjohn
    Joined: Nov 2009
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    glastronjohn Junior Member

    I'm repairing stringers and replacing the floor in my 20 year old boat. Should I replace the INCA plastic fuel tank? The tank looks good, but I have no idea what the average replacement age would be.

    If I do replace it, my model is no longer in production. My tank is rectangular with a V-shape angles on the bottom and is mounted in middle of the hull about 2/3 from the stern. The tank feed port is on the stern end and the vent port is on the bow end. Is this vent placement critical? Many similar sized tanks have the feed and vent on the same end of the tank. I'm afraid I might have venting issues when the boat is resting bow up in the water.
     
  2. gonzo
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    gonzo Senior Member

    I assume the tank was below deck. Unless there is some physical damage to it, you can reuse it. As long as the vent is on top, it works fine.
     
  3. glastronjohn
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    glastronjohn Junior Member

    Thanks gonzo. Reusing would definitely help the budget.
     
  4. marshmat
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    marshmat Senior Member

    Well built plastic fuel tanks (usually polyethylene) shouldn't deteriorate significantly over 20 years. If it's not cracked and not leaking, then as Gonzo says it should be OK to reuse. If you're not entirely confident in it, you could (with the tank EMPTY) hook a bike pump up to the vent and pressurize it slightly, which should make any pinholes or cracks easier to detect with soap and water or by monitoring a pressure gauge over several hours.
     
  5. brokensheer
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    brokensheer Senior Member

    I use plastic tanks in all my boats, you should not have a probrlem, however, The tank hold should be very clean and free from debris, ex an old screw can find its way through a good tank. I place all mt tanks on 1/4 neopreme blankets and are even built into there own hold so a leak if it were to happen would be contained

    also the USCG has new reg on open air around plastik tanks
     
  6. glastronjohn
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    glastronjohn Junior Member

    Good tips all around. I think I'll clean it, pressure test and look for leaks and worn spots. I've looked at least 30 different tank drawings and nothing is a good fit with the compartment size, bottom angle and feeder tube/vent locations.

    I've heard rumors that the somewhat new fuel in our area (10% ethanol mix) may cause tank problems. Does anyone know if this is true with older plastic tanks?
     
  7. marshmat
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    marshmat Senior Member

    Ethanol blend shouldn't affect a plastic tank at all; however, it does hold moisture better than regular gasoline. 10% ethanol has been around for a while, and while some folks absolutely hate it, problems are rare if you take proper care. The higher percentage blends can attack some older fuel hose and gasket materials, though.
     
  8. brokensheer
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    brokensheer Senior Member

    I had a few boats with fuel problems now they are on a fuel additive diet that included StarTron,,
     
  9. brokensheer
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    brokensheer Senior Member

    I looked this up for you the book is the code of federal regulation CFR.

    Federal regulations"
    drop down to ventilation and look up 33 CFR 183.630 ... you are looking for a natural ventilation regulation which is 183.630(5), and read the part about non-metallic fuel tanks. It will state what I have previously written above. A simple rule of thumb is the more air around the tank, the less likely that you will have to install the ventilation. If the airspace is tight, and the concentration of vapors exceeds the 1.2 g/cu. ft., you have to ventilate the space I.A.W. the regs.
     
  10. glastronjohn
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    glastronjohn Junior Member

    I haven't really thought about ventilation of the tank compartment. The compartment where the tank is installed is has .25 to.5 inch space between the tank and the stringers bulkheads. Just enough room for rubber padding. There's probably 3-4 inches space from the top of the tank to the bottom of the floor/soal with a 6 inch access covers above the feed port and another above the sending unit/vent hose port.

    This is concerning because the whole reason I started this repair was because of a small explosion the last time I used it. I filled up with fuel while on the trailer, drove to the ramp, turned on the blower and let it run while I backed down the ramp. When I "fired" it up, I heard a click, then whoomph. I opened the engine hatch sprayed the extinguisher. The explosion damaged the cuddy wood/fiber glass and flames singed some of the wiring above the engine.

    I drove it home and considered it a loss. I contemplated on donating it to charity. After a few weeks I decided to figure why it exploded. After gutting the interior and cutting out the floor I found that a jagged piece of fiber glass had cut through the tank vent hose. I'm lucky to be alive and I think the boat may be salvageable. My wife says even if I fix it, she still won't be going out on it. I can't say I blame her.

    You can see the cut vent hose in the 3rd picture: http://s363.photobucket.com/albums/oo76/harrije2/boat/
     
  11. gonzo
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    gonzo Senior Member

    Does your blower have a hose all the way down?
     
  12. glastronjohn
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    glastronjohn Junior Member

    The "in" blower hose ran to the top of the bildge/stern corner. The "out" blower hose was burnt to the wire. The blower hoses were a few years old.
     
  13. Fanie
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    Fanie Fanie

    Damn this sucks. Between Matt and Gonzo and the other guys they already said what I was going to :(

    All I could say is keep the fuel away from everything else. Not sure how the explosion started but that is a big no-no on a boat. Where the heck do you run to :D

    You fuel tank imo should be naturally ventilated, use good quality hoses. Some 'neopreen' I have found is quite shitty, they harden and crack after a while. I managed to get some industrial hoses which should last forever. It reeks of quality and not like these back yard mechanic **** you get from car spares places.

    You also have the option to put a SS braid over your hoses, it keeps the hoses from external damage, but I haven't used it before. My PE fuel tanks are around 13 years old, apart from some oiliness and dust they are ready to go.
     
  14. glastronjohn
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    glastronjohn Junior Member

    Yep. The 20 year old hoses I removed were dingy and poorly routed. But as I cut them up to put in the trash, the inner part of the hose looked nice and pliable.

    I purchased 13 ft. of 1-1/2" feed hose and 20 ft. of 5/8" vent hose from Jamestown. There's a small fortune in hoses sitting in my garage. When I replace the bulkheads I was thinking about glassing in 4 or 6 inch dia PVC pipe through the bulkheads into the bilge to make a type of conduit pipe for the rubber hoses to pass through. That should keep the hoses safe and easy to replace if needed.
     

  15. Fanie
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    Fanie Fanie

    Depends what PVC pipe, they fade in sunlight. If you paint them they will be ok. Darker (black) lasts longer in the sun than lighter colours (white or light blue) although more attractive - again unless you paint them to keep the sun out.

    As for the hoses, it's not only the sun perishing them, the fuel reacts with some rubbers and that is the biggest problem. Who knows what crap next they will throw into fuel to give it volume ;)
     
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