I did it. I was 19 or 20 years old, decking for my dad in Port A,, offshore charter out of Deep Sea Headquarters on a 31 Bertram. Yes, the fuel fill is right next to a rod holder. I was talking to someone on the dock with my head up my rear. My dad said I was white as a ghost when I walked up on the patio to tell him. He said he knew something was wrong when he saw me. It was 6 gallons.
We tied a rope on the bow and pulled boat over to an empty area of the harbour and went to work, opening hatches and hand bailing, then got a giant box of Tide and started cleaning.. After several hours of that we were done. had the cleanest bilge in town. Lesson learned, later on I went to work for a Hatteras,Bertram dealer. He always complimented me for how I checked bilges before starting an engine.
We were all aware of the consequences, It was back somewhere around 1964-66 When a boat at Woody's dock took on fuel. They had some sort of fuel fill line failure and had pumped like 40 to 50 gallons, Then they hit the started. I remember at least one was killed, all were blown out. boat burned to water line.
Serious stuff. Check those bilges