No, leaking gas is not normal...
Your fuel vent is equiped with a anti-sypon valve, its a little check ball that is housed in an aluminum, 90 degree hose barb thing that connects and vents out of the top of your fuel tank, it is connected to a 5/16" hose that runs above the gunwale (gunnel).
That little check ball can gum up pretty easy with todays high alcohol content fuel and winters storage. Anyway, when that little guy gets stuck closed, expanding air has to vent through the filler hose and gas cap, gas is comming out because it is above the trapped air in the tank, above the filler.
You should be able to access your fuel level sending unit and the anti-sypon valve fairly easy on an Enzo, Air Warrior or any other boat that has a V-drive, 06s and up all have the removable floor, zip out the 8 screws, disconnect the courtesy light, lift from the front and pull forward and the floor will come right out.
Remove the little guy, take him compleatly out of the boat and wash it out with WD40 and shake the crap out of it and repeat untill you hear the little ball shaking around in there, you should only be able to blow air in one direction when he is working the way he's suposto
The only other way you could be venting out of your filler will be if your vent hose is kinked or restricted