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Thread: Fuel Overflow

  1. #1
    Member Ebbtide's Avatar
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    Question Fuel Overflow

    Is anyone else having this problem.

    1. You fill the gas tank.
    2. The temperature heats up.
    3. Your boat starts dripping/running gas out the overflow.

    I know I could put less gas in the tank but how can you tell when you are 10 gallons from full? Is there some other answer?


    "Ebbtide" 27 X 9 GlacierCraft
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  2. #2
    Moderator stid2677's Avatar
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    I can only speak for my boat. I was having issues with fuel spilling out of the vent when backing the boat down the ramp and also when full on a hot day.

    I also had water get into the tank when storm driven waves splashed against the vent.

    I installed a 1/4 turn shut off valve between the tank and the vent and keep it closed unless I am filling the boat with fuel.

    My boat has 2 vents one at the filler neck and another at the rear of the tank.

    I have not had any problems since I did this mod.

    Good Luck

    Steve
    "I refuse to let the things I can't do stop me from doing the things I can"
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  3. #3
    Member alaskabliss's Avatar
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    I would be careful putting valves on the vents and keeping them closed. If you have a full tank of fuel and it gets hot outside, how much thermal expansion are you going to have and what kind of pressures are your tank going to see? I'm not sure if it is enough to matter but my thinking is that if you allow the tank to expand and contract over and over that it will get fatigued overtime and possible rupture. I think that is one of the reasons for the vent, along with displacing fuel with air when consuming fuel. Anyone else have any thoughts on this?
    Another way to look at it is what happens to a five gallon gas can when it gets warm out, it expands with the building pressure. I know it's plastic but the area is fairly small. My 80 gallon tank is alot bigger and I would think it would expand even more due to volume. Volume is more dangerous than pressure. For an example, 5 gallon can at 20 psi is less dangerous than 80 gallon tank at 20psi... I'm ranting, sorry, but I am really curious now about this. We need to find a smart guy who knows the formula to figure it out...

  4. #4
    Moderator stid2677's Avatar
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    Quote Originally Posted by alaskabliss View Post
    I would be careful putting valves on the vents and keeping them closed. If you have a full tank of fuel and it gets hot outside, how much thermal expansion are you going to have and what kind of pressures are your tank going to see? I'm not sure if it is enough to matter but my thinking is that if you allow the tank to expand and contract over and over that it will get fatigued overtime and possible rupture. I think that is one of the reasons for the vent, along with displacing fuel with air when consuming fuel. Anyone else have any thoughts on this?
    Another way to look at it is what happens to a five gallon gas can when it gets warm out, it expands with the building pressure. I know it's plastic but the area is fairly small. My 80 gallon tank is alot bigger and I would think it would expand even more due to volume. Volume is more dangerous than pressure. For an example, 5 gallon can at 20 psi is less dangerous than 80 gallon tank at 20psi... I'm ranting, sorry, but I am really curious now about this. We need to find a smart guy who knows the formula to figure it out...
    Remember I said I have TWO VENTS,,, the rear is to allow air to escape while filling. Use your own due diligence.

    Steve
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  5. #5
    Member alaskabliss's Avatar
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    Steve, I appoligize, I thought you were blocking both vents, My mistake. I'm sure you could understand my concern if you were blocking both vents...

  6. #6
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    Is the vent two low and needs to be raised? Did the builder put the vent outlet on the back of the fuel tank? You may need to add a one way valve to let the tank vent and also keep the water out. I do not know if putting a one wave valve in an air vent line is GG approved.

    I decided to ask a local boat builder the question about the one way valve, and he said yes it is and one brand is called “Lifeguard”. It a temporary fix because you can have problems using one. He then ask me why I was asking, when I describe the problem and said it was on a GC, did I get an ear full about the fuel inlet and vent mounted on the side of fuel tanks on GC boats. In case you’re wondering putting a vent or fuel inlet on the side of a fuel tank is not GC approve.

  7. #7
    Member Ebbtide's Avatar
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    I like the stopcock idea but I only have one vent and of course it is on the side. Not sure why it is not CG approved. May be that it has not been tested or maybe that it has been tested and failed. I personally don't see much diff as long as the vent is at the top of the side of the tank and the vent hose is angled up.

    Ideally you would know exactly how much gas is in the tank so you could shut the pump off 10 gallons or so before full. In reality this is difficult even with a flo-scan. Why is this not a problem in my truck??? The auto industry seem to have this problem worked out.
    "Ebbtide" 27 X 9 GlacierCraft
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  8. #8

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    Ebbtide,
    The trick is to listen when you are filling. You should be able to hear when the fuel is approaching the filler neck. You do not want to fill the neck until the pump clicks off. If you do that means that you have filled the tank and about four to six feet of filler line leaving no room for expansion at all.

  9. #9
    Member Ebbtide's Avatar
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    I have been playing around with the listening method. The problem is I fuel up in a lot of places and fuel pumps flow at different rates so all the whistles and wheezes are particular to each pump and rate. To compound matters sometimes its me doing the fueling and sometimes it is my son. I agree though, listening is probabley the most reasonabe answer. I just need to fuel and listen more consistently and could probably work this out. It does not help that I always want to jam as much fuel in as she will hold either.
    "Ebbtide" 27 X 9 GlacierCraft
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  10. #10
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    Quote Originally Posted by Ebbtide View Post
    It does not help that I always want to jam as much fuel in as she will hold either.
    It’s a problem all guys have.

  11. #11

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    Anyone ever use the Attwood P-trap fuel surge protector or one of their p-trap vents? I’m thinking of installing one of the two models for each of my tanks. http://www.attwoodmarine.com/store/p...urge-Protector

  12. #12

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    The surge protector will work for eliminating fuel discharging from your vents, however it will also close off your vent while filling and cause a gas geyser at your fill port. Make sure to never let the pump turn off itself.
    Install your fuel vents at the aft of your boat and it won't matter what kind of vent you use. If you install the vents on the side of your hull, make sure to have anti-siphon vents, otherwise in big water you will find you will get water in the fuel tank.

  13. #13
    Member jrogers's Avatar
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    I think there are two options to improve this; move the vent to a higher point or a longer distance with the vent hose, or install a larger diameter vent hose so that you have more volume to expand until you get to the overflow vent and are spilling. I don't think it is a training issue, but a design issue. I have had boats that do this all the time, and others that will never do it.
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  14. #14

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    While googling yesterday I discovered a marine fuel vent whistle. It attaches to the vent line close to the tank. When the tank is filled air escapes through the vent causing it to whistle. When the whistle starts gurgling or stops the tank is full. This should prevent overflow at the nozzle and the vent. I will be trying this this summer.

  15. #15
    Member Ebbtide's Avatar
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    Quote Originally Posted by overtime View Post
    While googling yesterday I discovered a marine fuel vent whistle. It attaches to the vent line close to the tank. When the tank is filled air escapes through the vent causing it to whistle. When the whistle starts gurgling or stops the tank is full. This should prevent overflow at the nozzle and the vent. I will be trying this this summer.
    Cook inlet keepers was giving them away at the Sportsmans show. I picked one up and will be installing in the next couple weeks.
    "Ebbtide" 27 X 9 GlacierCraft
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  16. #16

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    Quote Originally Posted by Ebbtide View Post
    Cook inlet keepers was giving them away at the Sportsmans show. I picked one up and will be installing in the next couple weeks.
    Yeah i got one from that booth too!

  17. #17
    Moderator bkmail's Avatar
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    Snagged one as well. Will install it on the airboat fuel line.
    Bk
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  18. #18

    Default Fuel Overflow

    The whistle is pretty darn loud!


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  19. #19
    Member Rob B's Avatar
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    Dang it. Wish I had seen these at the show
    27' Wooldridge Super Sport Offshore Pilothouse PRIME TIME!
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  20. #20

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    Quote Originally Posted by Rob B View Post
    Dang it. Wish I had seen these at the show
    They sell them at west marine in anchorage. I think they are around 30$

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