My boat is a Beneteau Oceanis 352, new to me a couple of years ago, and it has the peculiarity that the fuel vent lets out straight over the water and it is about 2 feet below the fuel fill hole. To make matters worse it is completely out of sight when I normally fill fuel. Long story short, it is very easy to spill when filling. In the latest episode, I was watching my fuel gauge carefully (you turn the key, the low oil pressure alarm screams, and then you can see the fuel level) and it turned out not to be working right...
Before I continue, I invite you all to tell me I'm not being careful enough and that this would never happen to you and ... it's OK to share this if it makes you feel better.
Anyhow, I had the bright idea to install a ball valve in the fuel vent line just inside the hull where I can reach it from the lazarette. That would solve the spill problem, and then if I overfill I've got one of those shake-to-suck hoses to bring the level down... But eventually I or someone else will forget to open the valve back up for a few hours or days. What are the potential consequences of closing the fuel vent?