Questions about adding Fuel Tank Venting

Discussion in 'Powerboats' started by jtarkington, Oct 4, 2009.

  1. jtarkington
    Joined: Oct 2009
    Posts: 1
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    Location: North Carolina

    jtarkington New Member

    Just found this forum while trying to make some changes to my boats fuel venting.

    I currently have a boat that has a vented fuel fill, the vent is built into the fill. I want to add an external vent so I can utilize a locking fuel cap, the only ones that I can find are for non-vented fills.

    I need some experienced guidance on a few questions:

    The boat is a 20ft I/O with a 36 Gal fuel tank.

    1. Does the external fuel vent have to be a certain size? (Purchased a Attwood flush stainless with a 90 degree elbow, seems rather large)

    2. I see from other posts that a loop is recommended to keep water out, is this just a rise of the vent hose past the vent and back down or are they speaking of a true full loop like the letter "O" above the vent before connecting the vent hose?

    3. The vent should be mounted above the height of the fuel fill correct?

    4. Ok to mount vent on the side of the boat as opposed to the transom?

    Thanks in advance for any help,
  2. mark775

    mark775 Guest

    There is hose rated for gas/fire. I remember it being Parker with red writing but don't remember. You want a large vent. Just a rise. It is best if the vent is above the fill but necessarily above the fuel level. The side of the boat is out, IMO, unless you don't mind water in the fuel.
  3. TerryKing
    Joined: Feb 2007
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    Location: Topsham, Vermont

    TerryKing On The Water SOON

    I have built two boats with the vents on the sides, opening facing aft and a little down, about 2 ft above waterline.

    Never any problem with water in the fuel...
  4. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    I've had the aluminum fuel tank replaced because seawater ate through the bottom. During later inspections I've actually seen through the gasoline drops rolling over the bottom. The fuel tubes do not quite reach the bottom so the water is not sucked up and has ample time to corrode the metal.

    Side mount, 2 ft above the waterline is the way the industry has mounted fuel vents on recreational boats for as long as I can remember. Obviously you are not supposed to anchor or use your boat in waves over 2 ft.

    There are vents with a small neoprene ball that reduces the chance of water entering, but given time the ball gets sticky and clings to the grate.
  5. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The vent hose has to be the same marine type fuel hose. A loop will prevent water from entering. It only a rise on the hose. The higher the better.

  6. Submarine Tom

    Submarine Tom Previous Member

    1/2" inside diameter hose, higher the better.
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