I have a friend that had an older Starcraft with a fueling setup like yours. He had trouble several times with water in his gas - I had to tow him in twice - cost him a lot of money. Turned out his side vent cap was forward of his his filler cap and the vents on the bottom were facing forward - when he ran in rough water the spray would go right in thru the vent and into his gas tank. Make sure the breather vents are facing toward the stern. He took his boat to marine repair shops to have the gas pumped out, carbs rebuilt, water separator installed, etc, $$ - all said BAD GAS - BS. Only to happen again. We finally figured it out while drinking beer after towing him in - very disappointing when you think about it.