I also have to fill fuel in the engine space. When I transfer fuel at sea I can do it down below and not worry about water getting into the fill. Actually, I have a transfer pump and filter system that is plumbed right into the top of the tank. There is a 15 foot hose connected to the pump that I can drag out to the cockpit and suck the fuel out of the Jerry jugs. If the jugs are on the side deck, I can run the hose out the galley porthole and do it that way. Everything gets filtered prior to going into the tank. Boy, you would not guess the amount of crap that ends up in the bottom of the Jerry jugs. I have a cap on the top of the tank which i can open and look right down into the tank if I want to fill that way. I never have but I could if the need ever presented itself. I have three water fills. One at the bow and one on either side. The fuel fill caps and holding tank are on the port side and the rum is on the starboard side.