Jack Campin wrote: Is somebody extracting the michael?

It does sound that way, but the name Billy of Tea is also problematic. The Australian National Dictionary cites only one use of "billy"-as-in-billycan prior to 1849 (although that one use was in New Zealand). The Otago whaling operation shut down in 1841.

There is no time for a Weller Brothers to have had a ship called the Billy of Tea. It's an anachronism.

Not the biggest problem with the song, to be sure, but if one is going to claim the song as from the Weller Brothers era, it's something that has to be explained.