You could have a fill line leak but you could also have a leak at the sending unit gasket. Next time you need fuel, BEFORE you fill up, clean the area around your sending unit and then leave DRY paper towels around it. Fill the tank all the way up and either run the boat if you filled up with the boat in the water or trailer the boat a few miles if you filled up with the boat on the trailer. Now inspect/ SMELL those clean paper towels you left around the sending unit and see/smell if they're damp or smell like gasoline. If those towels are damp or smell like gasoline, you might still have a bad fill or vent line but you’ve also got a leaking sending unit gasket.
As for replacing the fill line. Here is how I did it on my 2005 Parker 2520. Remove the screws attaching the stainless steel fill nozzle fitting to the gunnel . There may also be a ground wire also attached to that fitting At the fuel tank remove the hose clamps. I used a pair of pump pliers to twist the rubber hose off the fuel tank. Wiggle the stainless fill nozzle fitting out of the gunnel. I securely taped a piece of line to the hose at the tank end and pulled the fuel line out through the hole in the gunnel where the fill nozzle was. You have now pulled that attacked line from fuel tank, up to the hole in the gunnel where the fill nozzle was. Securely tape that same line to your new fuel fill hose, have a helper feed the hose in the hole in the gunnel as you pull the line from the end at the fuel tank. Connect and clamp the new fill line to the fuel tank, attach other end of the new fill line to your fuel fill nozzle, screw the nozzle back in place, reattach ground wire.