Given that the song says that the Mary Ellen Carter was a fishing boat that carried a crew of around five or six, it would make her a vessel of around 30 to sixty feet long depentant on which fishing grounds she worked,

Since the song says that she sank after hitting Three Mile Rock and she lay at a diviable depth, its likely she was working te coastal fishing grounds, In which case the rock was proberly a local reference rather than one that would be found on a navigation chart.

Since the Mary Ellen Carter was a fishing boat around thirty to sixty feet long so that she would have not been listed in any register of shipping. It is a common practice world wide to name fishing boats after a Wife or a Mother.

So to see if she was real do a seach on a "Mary Ellen Carter" as a real name, rather than a boat and that may lead you in the right directions.

BTW also do a backgroung search on Stan to see if a "Mary Carter" was a part of his life.

Bruce D