Gas fill deck fitting

[Kevdon22]

I have a 21foot Aquasport IO with a gas fill deck nozzle that has the vent connected to and under the fill nozzle.
It seems to vent well when running but backs up during filling often allowing gas to enter the vent line preventing adding more fuel.

I don't understand how it vents since I don't see a large external hole that might allow rain to enter into the deck fill. In either event it does not seem to be working properly.

How does this work and can it be repaired?
Appreciate any comments, Thanks.

 

[Sandy]

No idea whether your deck fill is made by Attwood Marine , Perko or another, but here is Attwood's technical description page:

http://www.attwoodmarine.com/userfiles/store/product/files/1280/a-pvdf-08.pdf

http://www.attwoodmarine.com/store/product/plastic-deck-fills

At least some earlier versions of vented deck fills were known to allow some water intrusion with bad results. But Attwood claims their newer ""water-proof"" screen in the vented cap is effective at keeping it out. Maybe similar concept to Gore-Tex or Racor separator media?

Can you check to ensure there is no vent hose dip/trap holding fuel and not allowing any fuel which gets pushed in there to drain right back down into the tank?

 

[Brite Idea]

My brother-in-law bought a boat two years ago and had the same problem it turned out that there is a fuel spill preventing valve right below the deck fill that was not opening. We removed it and replaced it with a piece of pipe and problem solved. It could also be a blocked or kinked vent line.