During the 1960s in Melbourne -- I remember being told, by a folklorist who performed this song, that Johnny was indeed press-ganged. He didn't explain how he knew this and I was far too shy to ask. The idea got filed away in my head though.
I've always loved the sweet innocence of the girl with her picture of her handsome young Johnny, with his golden hair against his blue jacket, who will be a captain one day. (Of course he will:-( )
It's such a contrast to the reality of life at sea at the time.

Now I have the picture of Little Marion singing from an unamplified mid-19th century stage. Many of the men in her audience would have been sailors who'd jumped ship. They knew the life at sea well. She made strong men weep -- and no wonder.
Cheers, Joy