... There always is an option of crewing a level 2 person, then ask the to join the Boss Battle.
When you get on the ship and the navy men lvl 30+ attack the other pirate, then you'll be the only one, making you the one captaining the ship, and aiming at the bridges and the Goliath at the end
But you obviously would not be able to live with yerself after getting a friendly pirate sent to jail, even if ye are a pirate
So, ye could do what I said above with another computer/ laptop and a second pirate on a different account, living with the fact that you killed yerself 2 times because you probably wont get passed the Navy at the beginning.
Or, you could do the sensible thing, and gather up a crew of high lvl people here on the forums or out on Tortuga, and have them do it with you.
Take yer pick, mate
See ye on the high seas!