not a clue

[unclemac]

y'all should get this right quick but I sure can't...found on a beach, made of brass and that rubber looks pretty much from a bygone era. don't have a clue....anybody?

 

[BIGSCOTT]

fuel port for a boat

 

[unclemac]

...see? I knew y'all would get it fast....so the nut came off?....how old, what kind of boat do you figure?