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  1. #1
    Seaman
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    Default Does Gas Vent Prevent Water?

    Went to pull my boat out the other day and sunk the back end of my boat with my 80 Merc 2/3's under the water after the trailer sank in some muck. An hour went by before we could get it out so I am wondering would my gas tank vents prevent water from getting in the tank? Its a round chrome vent that sits up about 1/2 an inch with 2 holes in the side. What do you call the stuff that checks for water in gas? Thx for any help.

  2. #2
    Captain Philster's Avatar
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    Default Re: Does Gas Vent Prevent Water?

    If it is looped, the vent line can prevent water, but if it was submerged more than a foot or two, then it could have taken on some amount of water. There is no mechnansim to prevent water from entering; the loop in the vent line is meant to do that, but if the loop itself is fully submerged, then some water can get in.

    boat059.jpg

    How far below the waterline did the vent go?

    Ethanol can absorb some am't of water and it can be burned without a problem. It might be the only up side to ethanol. The downside is that if there is too much water, then you get phase separation and need to test the fuel by taking bottom samples. It would be all water at the bottom. Not good to see.
    Checkmate 2400BRX/Optimax 300xs
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    Alumacraft 17 w/ Merc 40 4S

    Date an I/O, but marry an outboard!


  3. #3
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    Default Re: Does Gas Vent Prevent Water?

    assuming it's the vent on the side of the hull: water may have gotten in there. the hose inside the vent is supposed to be "swan neck" which is an up-side down version of the trap under your bathroom sink. But some boats skip this, or it's so slight that it wouldn't keep out that kind of pressure.
    If you have non-ethanol gas the water should settle to the bottom; ethanol gas and it is mixed up in it (eventually seperates into sludge). Pull the cap over the sending unit, and do the soda-straw trick: stick a clear tube straight to the bottom, thumb it closed, pull out, see if there's a layer. empty into a clear bottle and observe.
    Or disconnect the fuel line at the motor, remove the fitting, pump some gas into a clear bottle, observe. Of course a water seperator will make this test unreliable, and a seperator can't handle a gallon of water on the bottom.

    How much gas is likely contaminated?

    PS another reason not to sink a trailer
    A man of constant boat tinkering.

  4. #4
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    Default Re: Does Gas Vent Prevent Water?

    Yes sinking was not good but the water level was down so we had to back in further to load the boat and thats when the trouble started. Loaded the boat many times at the same spot but the water was a foot higher. Not a pretty sight so be careful.

  5. #5
    Senior Chief Petty Officer spoilsofwar's Avatar
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    Default Re: Does Gas Vent Prevent Water?

    Not to get horribly off topic, but why were your transom tie downs on at that point? And if they weren't, I don't see how the boat would sink along with the trailer. Maybe I'm missing something?
    2012 Stingray 195CX / VP 4.3GL

  6. #6
    Lieutenant Commander NSBCraig's Avatar
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    Default Re: Does Gas Vent Prevent Water?

    Takes 1% water to completely separate gas and ethanol.

    It will not re mix and will not run through your motor without causing damage.

    How much is in there, maybe you should drain it.
    1982 Baja 16ss

  7. #7
    Seaman
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    Default Re: Does Gas Vent Prevent Water?

    I am in the process of draining it through the gas line. Got a gallon of water out then it turned back to mixed gas so I am letting it sit for a while and I will try it again. No it was not tied down,we were getting it out and it wasn't centered so I backed in again and when I went back to check it had already sank maybe because it was already pulled up tight to the front...no idea. Like I said it wasn't a pretty sight and I was shocked at what had happened. You know...Dear in the headlights and you don't know what to do,Van won't pull it out because its full of water. Thx again for all the help everyone.

  8. #8
    Captain Philster's Avatar
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    Default Re: Does Gas Vent Prevent Water?

    Yeah, I'm still not seeing how it sunk. Did you go so far back you submerged the front (being that you say only the front was tied town to the winch), then it filled with water and was up to the top deck with water?
    Checkmate 2400BRX/Optimax 300xs
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  9. #9
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    Default Re: Does Gas Vent Prevent Water?

    Looks like you have water.
    The fuel pickup tube ends 1 inch above the bottom of the tank to prevent picking up bottom crud and water.
    So you will not get the last inch out using that method.

    Pull the fill hose and siphon out all the water you can get.
    The fuel (minus the water) is still usable.
    The little water still in the tank will re-dissolve as you add fresh fuel.
    10 gallons of fresh E10 gas can absorb up to 6 ounces (3/4 of a cup) of water.

    The Stuff you were looking for is call Water Paste.

  10. #10
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    Default Re: Does Gas Vent Prevent Water?

    Quote Originally Posted by MMHagler View Post
    I am in the process of draining it through the gas line. Got a gallon of water out then it turned back to mixed gas so I am letting it sit for a while and I will try it again. No it was not tied down,we were getting it out and it wasn't centered so I backed in again and when I went back to check it had already sank maybe because it was already pulled up tight to the front...no idea. Like I said it wasn't a pretty sight and I was shocked at what had happened. You know...Dear in the headlights and you don't know what to do,Van won't pull it out because its full of water. Thx again for all the help everyone.
    1. if you got a gallon of water out, don't try to save that fuel. How big a tank/how much in it? there are companies that will pump it out and dispose of it; some will clean it, You can trailer the boat to them.

    2. Boats can swamp on a trailer at a ramp if the bow is high enough, especially with tilt trailers or a steep ramp. Dropping one wheel off the end of the ramp, with the other still high, can do it. Also a boat with a lot of stern weight (full coolers, etc.) can be at risk--which is why for some launches, you load the boat after you launch (yes I know at a crowded public ramp you don't do this).
    A man of constant boat tinkering.

  11. #11
    Master Chief Petty Officer
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    Default Re: Does Gas Vent Prevent Water?

    Quote Originally Posted by UncleWillie View Post
    The little water still in the tank will re-dissolve as you add fresh fuel.
    I'd double check that fact. Adding fuel will dilute the amount of water, by reducing the ratio of water to fuel. This can improve things, however gas and water do not mix. Water won't simply 'dissolve' into the fuel.

  12. #12
    Seaman
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    Default Re: Does Gas Vent Prevent Water?

    Thx Home Cookin' and Shrew. That sounds like exactly what happened and the muck really helped. Thats why I come here when I need to know. Won't happen again. Tank is drained,new batch is in and I am off too a different launch. Thx very much.

  13. #13
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    Default Re: Does Gas Vent Prevent Water?

    Quote Originally Posted by shrew View Post
    I'd double check that fact. Adding fuel will dilute the amount of water, by reducing the ratio of water to fuel. This can improve things, however gas and water do not mix. Water won't simply 'dissolve' into the fuel.
    If we are talking E10 gasoline, It Absolutely will!

    Easily demonstrated.
    Take a quart jar, Add 8 ounces of E10 gasoline.
    Add 10 drops of water, notice that it pools on the bottom.
    Seal and shake the jar. The water dissolves. Gone! Clear gas!
    Repeat his 3 to 5 more times.
    Eventually the water and alcohol in the fuel will drop out of solution. (Phase Separation!)
    The fuel will now be very cloudy with a layer of water on the bottom.

    Now, Add another 8 ounces of fuel.
    Seal and shake again. The Phase Separated Water and Alcohol Re-dissolves. Clear fuel again!

    This is one of the fuel myths that keeps getting repeated, nobody questions, But is NOT True!

  14. #14
    Petty Officer 1st Class
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    Default Re: Does Gas Vent Prevent Water?

    Tough luck! A fuel filter/water separator is a nice thing to have. Racor makes a really nice one for an outboard with a clear bowl on the bottom. Mount it somewhere in your splashwell and just drain the water out. Mine came with two inputs, so I added a couple of valves and hooked up a small 6 gallon tank. That way if I ran out of gas, I'd have an auxiliary tank.

    http://www.amazon.com/Racor-320R-Rac...5904426&sr=8-7

  15. #15
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    Default Re: Does Gas Vent Prevent Water?

    Quote Originally Posted by CaptOchs View Post
    Tough luck! A fuel filter/water separator is a nice thing to have. Racor makes a really nice one for an outboard with a clear bowl on the bottom. Mount it somewhere in your splashwell and just drain the water out. Mine came with two inputs, so I added a couple of valves and hooked up a small 6 gallon tank. That way if I ran out of gas, I'd have an auxiliary tank.

    http://www.amazon.com/Racor-320R-Rac...5904426&sr=8-7
    Racors may be great but they can't be used to extract a gallon of water from a tank.
    A man of constant boat tinkering.

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