Hey Capt. cool name,
Either someone secretly filled your tank or you need to inspect all three gas veins. Obviously the fill should be the biggest hose. It should have a fairly straight path down the gunwale across the deck to the tank. I'd stick a long, smaller diameter hose in it at the fill tube and see if it has any trouble reaching the gas tank (you know, like when you're trying to get some gas out of your Uncle's truck
). There may be a loop in the fill hose or maybe something got in there, but even so, if it were blocked the fuel would likely back up and flood at the fill hole.
The vent elbow is probably next to the fill elbow, and its hose will run toward the vent - it could have a clog that creates an airlock where maybe a pocket of air is just pushing a bit of trapped gasoline out, or maybe there is just some gas sitting in a low spot that is forced out when any comes in thru the fill. Or maybe a chunk of sealant dissolved or broke free and floated into the vent tube. You might start by disconnecting the vent hose at the tank and see what drains out when you force air back down it from the vent. Have a jug ready to catch the gasoline or whatever. And "no smoking" around you...
Obviously, this could happen on the supply hose between the tank and engine, especially at brass elbows. Check your fuel/water separator to see if you find any crap in there.
Sealants for sending units have changed in chemistry over the years as has fuel. I found chunks of silicone were clogging my fuel lines. Someone probably replaced a sending unit and used silicone for a gasket, and modern gas with ethanol probably broke it down causing me grief. Here is a pic of that:
Look into it now before the fishing really goes off.
Good luck and let us know what you find...