Below is the fueling system I built for trips to Catalina Island in the Potter-15.
We leave a dawn and the trip to the tip to the island takes six hours at hull speed and the winds don't really come up until we are about 3/4 of the way. So you want to keep things moving with the help of your trusty outboard.
This gas tank fits nicely at the back of the cockpit and holds enough gas to get you to the island and back (without wind) with gas to spare.
The shut off valve is an important thing to have, without it you run the risk of having the line fall into the boat (un-noticied) and set up a siphon of raw gas into your cockpit. Don't ask me how I know this but lets just say it's a good thing I don't smoke.
When you are halfway to Catalina you don't want to let the motor starve and die so you wind up hanging over the transom with a small gas can trying to fill the motor while the fleet moves on. Additionally, you risk the motor "hard starting" while your imagination start running with"what the H do I do" if this thing won't start?
For peace of mind just watch your trusty wristwatch and pump the tank full (about four squeezes on the bulb every half hour.
Also works great if you have to help a fellow Potter Skipper by pumping some gas into his empty 3 gal gas can?