Originally Posted by nunzio
New boat and my first fill up. Good point about the fast fill although we were trying to fill slowly. Question: Where is the vent line connected. Is it the fill ine or the furl tank? I think my first note could be wrong that the thiord line on the tank id a "return" line and not the vent which means the vent line may be tapped off the fill line.
Usually the vent line is tapped right into or near the top of the tank, then leads from there up to a high point in the hull or side of the coachroof.
The return line is for excess fuel that the fuel injection system does not use, so it gets pumped back to the tank from the injectors. You should be able to trace that line fairly easily. There should also be a fourth line, for fuel delivery coming from the tank to the fuel filter/pump. It will look much like the return line.
Now that I know this boat is new to you, and assuming you weren't using a high-speed pump, my hunch is that you have a low-point in the fuel fill line. Go down to the tank and see if the fuel fill line dips down a bit below the fitting where it attaches to the tank. If so, that is the culprit and you can try to fix it or live with it by pumping slowly. Sometimes there's no way to route that fill line without it taking a little dip before it gets to the tank.