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Thread: fuel fill vent

  1. #1

    Default fuel fill vent

    has anyone ever had water get in through the fuel fill vent on the side of the boat in real rough waves.
    It's not the heat, It's the lack of air conditioning!!!

  2. #2
    Petty Officer 2nd Class
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    Default Re: fuel fill vent

    I haven't, but I could see how it might happen on my boat, given the placement of vents.

  3. #3
    Petty Officer 2nd Class gene8084's Avatar
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    Default Re: fuel fill vent

    I'm seriously considering that's how I got water in my tank. I completely drained it two years ago. I store it in doors... hasn't been rained on. I store it full of fuel...with stable. Yet tonight when I pulled my fuel/water separator, there it was 1/4" out of 3-1/2" sitting on top.

    If it's not from rough water and the vent, it's getting in the vent when I hose it down.
    Gene Brown
    ..................................
    1974 Thunderbird Formula 180,
    Mercruiser 888, Ford 302, Holley
    1958 Rhones 18 (winter project)

  4. #4
    Moderator Bondo's Avatar
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    Default Re: fuel fill vent

    Ayuh,... That's Why there has to be a loop Up, before the line drops down to the tank....
    Yet tonight when I pulled my fuel/water separator, there it was 1/4" out of 3-1/2" sitting on top.
    As I noted on Your thread,.... Gas floats,+ Water sinks....
    Any Grease is Better,..... Than No Grease at All.......

  5. #5
    Petty Officer 2nd Class gene8084's Avatar
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    Default Re: fuel fill vent

    Quote Originally Posted by Bond-o View Post
    Ayuh,... That's Why there has to be a loop Up, before the line drops down to the tank....
    Can you explain what that means "Loop Up and how it works?
    Where would the loop be?
    Does this prevent suction from the fuel sloshing around in the tank?

    I don't believe my setup has been modified since it was built, although I think they replaced the vent tube fitting at some point. I found the old one in a box of parts I got from the previous owner. The replacement appears identical.

    All that said, ... not saying the original setup in 1974 was correct. There is a fill cap on the starboard side with a 1-1/2" fill hose that drops on a slight angle down and disappears below deck. There is a 3/4" vent hose that runs parallel to the fill hose. Neither are visible or accessible without a complete tear up of the deck.

    There's no loop in the line before it runs below deck.

    A picture of it done right would be great!
    Gene Brown
    ..................................
    1974 Thunderbird Formula 180,
    Mercruiser 888, Ford 302, Holley
    1958 Rhones 18 (winter project)

  6. #6

    Default Re: fuel fill vent

    You want the vent line to run" uphill" from the vent before going "downhill" to the tank.

  7. #7
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    Default Re: fuel fill vent

    The tube is called a "swan's neck" and is essentially like a drain trap under your sink, upside down. Water entering the vent runs back out ratehr than crossing over the top and into the tank.
    I lost a motor this summer ( and might have lost he replacement) from this. My vent was old, had some chips and corrosion I hadn't noticed, and when I opened the access hatch found it didn't have a swan's neck, just a direct line.

    I replaced the whole thing with an internally vented fuel cap. This boat has very low freeboard anyway and the vent, located close to the bow, can go under when the boat dips--like when you stop with people sitting in the bow area.

    Typical boating: a $10 part can cost you a $X000 motor.
    A man of constant boat tinkering.

  8. #8
    Petty Officer 2nd Class gene8084's Avatar
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    Default Re: fuel fill vent

    Quote Originally Posted by metriccrescentwrench View Post
    You want the vent line to run" uphill" from the vent before going "downhill" to the tank.
    Mine definitely doesn't do that

    But, sounds simple enough. I was picturing an actual loop, which I guess is not a good idea because it would hold water (like a trap in the sink) keeping the vapor smell in the tank, but preventing breathing.
    Gene Brown
    ..................................
    1974 Thunderbird Formula 180,
    Mercruiser 888, Ford 302, Holley
    1958 Rhones 18 (winter project)

  9. #9
    Chief Petty Officer Woodnaut's Avatar
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    Default Re: fuel fill vent

    I definitely had water enter both fuel tanks through the tank vents. The vents were located directly under the rub rail and closer to the back of the boat than the front. Ripping around offshore there was a lot of splash and I managed to get enough salt water into the fuel to make it past the in-line filter, HP fuel pump and eventually trash 3 of the 4 injectors. (But I replaced all 4. 2006 Yamaha F90.) What a mess.



    I moved the vents from the side of the boat to the motor well in the back. The tanks were near the back so this was an easy move. I did that two years ago and the fuel has stayed clean and water free ever since.


  10. #10
    Moderator Bondo's Avatar
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    Default Re: fuel fill vent

    Ayuh,.... Vent _/\
    .........................\_ Tank...

    I was picturing an actual loop, which I guess is not a good idea because it would hold water (like a trap in the sink) keeping the vapor smell in the tank, but preventing breathing.
    As long as the Loop is Upward,.. It'll drain just fine...And properly vent as well...
    Any Grease is Better,..... Than No Grease at All.......

  11. #11
    Petty Officer 2nd Class gene8084's Avatar
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    Default Re: fuel fill vent

    Thanks everybody.

    I feel a little better now that I understand how it happened. I remember slamming into some large wakes that soaked us in the boat last time out and I suspect that's when she siphoned the water in. It probably sloshed around for the rest of the ride, then settled out nicely around the pickup over the week. The rest is history.

    I crawled into the bow and see I have very little room to gain any height for an up hill loop with the vent hose. My local shop that knows the Formula 180 suggested this.

    http://www.attwoodmarine.com/store/p...Fuel-Tank-Vent

    Anyone ever try this? Looks pretty straight forward for $12.00.
    Gene Brown
    ..................................
    1974 Thunderbird Formula 180,
    Mercruiser 888, Ford 302, Holley
    1958 Rhones 18 (winter project)

  12. #12
    Fleet Admiral Mark42's Avatar
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    Default Re: fuel fill vent

    Quote Originally Posted by Woodnaut View Post
    I definitely had water enter both fuel tanks through the tank vents. The vents were located directly under the rub rail and closer to the back of the boat than the front. Ripping around offshore there was a lot of splash and I managed to get enough salt water into the fuel to make it past the in-line filter, HP fuel pump and eventually trash 3 of the 4 injectors. (But I replaced all 4. 2006 Yamaha F90.) What a mess.



    I moved the vents from the side of the boat to the motor well in the back. The tanks were near the back so this was an easy move. I did that two years ago and the fuel has stayed clean and water free ever since.


    I'm sure it works well to keep the water out of the vent. BUT, be aware that having the vents in the splash well is in violation of coast guard regs. The fuel system for fill and vent must be installed in the boat so that any overflow runs OUTSIDE the boat. The coast guard specifically states that the splash well is considered INSIDE the boat. Gas often shoots out the vents when filling the tank.

    Just an FYI...

    BTW, nice boat!
    1985 Bayliner 1600 Capri Cuddy, 1965 MFG Niagara Custom. >> MFG Video<<. >> MFG Project<< >>Bayliner Hard Top Project<< >>Bayliner Repower Project<<


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