I have a 25 C-Hawk with the Perko fuel fill/vent combo and everytime I gas up at a marina pump, the vent spits out after a few gallons, then settles down for the balance of the fill-up. But, the kicker is that it will never allow me to get to within 7 gallons of the full 110 gallon tank. I can see the fuel in the fill line looking full to the top, yet I know there are 7 gallons remaining. If I don't use a gas dock and use 5 gallon cans instead, let's say when I'm down 20 gallons, I can get all 20 gallons in. I've tried just barely pressing the handle at the gas dock, cannot seem to get around the issue. Is it purely a breathing/vent issue when the vent is part of that combo fuel fill/vent perko unit? would it be better to have a traditional vent line to the side of the boat, separate form the fuel fill cap?