Re: fuel fill vent
The tube is called a "swan's neck" and is essentially like a drain trap under your sink, upside down. Water entering the vent runs back out ratehr than crossing over the top and into the tank.
I lost a motor this summer ( and might have lost he replacement) from this. My vent was old, had some chips and corrosion I hadn't noticed, and when I opened the access hatch found it didn't have a swan's neck, just a direct line.
I replaced the whole thing with an internally vented fuel cap. This boat has very low freeboard anyway and the vent, located close to the bow, can go under when the boat dips--like when you stop with people sitting in the bow area.
Typical boating: a $10 part can cost you a $X000 motor.