I was hoping to read a solution to this problem by now...but alas....I see
head scratching still going on....
How can you own a boat and not know what stuff is.....or why it's there.....etc..etc..
I still think the threaded pipe may have been the original fill point for the tank in the keel...but since closed up and used as a location for the
fuel return line...and a new fill location is located elsewhere....
But will readily admit my guesses are as good...or as bad....as anyone else's..