So, ship combat is incredibly trivial once you get the hang of it.
My ship is clearly inferior and I still feel like I can defeat EVERYTHING with a little bit of luck, and otherwise getting into range asap, then hold -> fire -> jibe -> hold -> fire -> jibe -> ... forever with the starting ship until the enemy inevitably dies. I also always go for the hull, fuck everything else. I cause a shitstorm in their ship pretty quickly with the standard cannonball shot.
The ship I defeated had like 4 cannons on each side, and I still fucked it up using the strategy I mentioned above. I don't know how much tougher ships can get, but right now I feel invincible with the starting ship and iron thunderer cannons.