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How to install the gas tank vent

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jbyers
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How to install the gas tank vent

Post by jbyers » Fri Jul 15, 2016 9:27 pm

I am about to put a new gas tank into my 58 cavalier. This may sound like a strange question, but as I got to thinking about the copper vent line I started to doubt whether the U "trap" should face up or down. It was facing down when I took it out, but there is evidence that the line has been removed and replaced at some point in the past.

On first thought it seems obvious that a trap (if that is the actual function) should be facing down like a plumbing trap. However when I got to thinking about it, if the trap is facing down then there are a couple of scenarios that would result in the trap filling up with either water or gasoline. If it did, then I would think that the fuel pump would not be able to overcome the eventual vacuum within the tank resulting from the inability of the vent to draw air as intended. At that point you would have a gas starvation at the carburetor.

On the other hand, if the "trap" faces upward then any gasoline that might slosh up into the copper tube would most likely drain back into the tank. Any water that enters through the screen vent on the transom (either from lake water or accumulated condensation)
IMG_1890.JPG
would likewise drain back out through the transom vent.

So which configuration is correct............ Be gentle please....... :mrgreen:
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Captain Nemo
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Re: How to install the gas tank vent

Post by Captain Nemo » Sat Jul 16, 2016 6:43 am

Up
Boats are to be made of wood, otherwise, God would have grown fiberglass trees.

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quitchabitchin
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Re: How to install the gas tank vent

Post by quitchabitchin » Sat Jul 16, 2016 8:55 am

Up. If it is installed down, it will fill up and the pressure in the tank will blow it out the vent on the transom, you don't want that. It goes up to prevent the fuel level from being high enough to run out the vent. In fact, on my boat, I had to make mine go even higher, but it still spilled fuel when the tank was full, so I installed an aftermarket one higher up on the deck.
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jbyers
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Re: How to install the gas tank vent

Post by jbyers » Sat Jul 16, 2016 6:09 pm

IMG_1896.JPG
Thanks you two....... I have it installed as high up as possible. You can't see it in the picture but the top of the U is hitting against the underside of the rear deck.

So after sitting around for a year, here is my new Jayco Manufacturing gas tank...........
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Captain Nemo
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Re: How to install the gas tank vent

Post by Captain Nemo » Sat Jul 16, 2016 7:05 pm

Looks nice! :)
Boats are to be made of wood, otherwise, God would have grown fiberglass trees.

jbyers
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Re: How to install the gas tank vent

Post by jbyers » Sat Jul 16, 2016 7:23 pm

Thanks Nemo............ now I just need to get it running again and finish prepping it for paint.

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Bilge Rat
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Re: How to install the gas tank vent

Post by Bilge Rat » Mon Jul 18, 2016 1:13 pm

I had Jayco manufacture a new 50 gallon tank for me. Too pretty to hide behind the seat! I had more room above the tank in my boat so I used a Racor Lifeguard fuel/air separator in the vent line. Haven't had a problem with fuel spilling out the vent and ruining the varnish or the waterways.

https://www.parker.com/literature/Racor ... SL0184.pdf

Regarding how you found the bend going the wrong way, there's an old adage... "Just because you found it that way, doesn't mean its supposed to be that way".
1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

jbyers
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Re: How to install the gas tank vent

Post by jbyers » Mon Jul 18, 2016 6:43 pm

Yeah, it's a shame to hide it for sure........ I'm just glad I thought it out and asked the question instead of putting it back in like I found it.

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