who and what are in "gallipot of a boat" ?

The gallipot means a small unstable boat. This was in chapter 17. Unfortunately, the men have a very difficult journey ahead of them and struggle returning to land because the small boat was overloaded and it was going against the tide. Five men were in it: Trelawney, Redruth, and captain included. Even more dangerous, the current pushed them to come ashore precisely between Silver's two boats. Added to these problems, the captain spots the biggest dilemma of all: Silver's men are removing the tarp from the cannon and they realize they did not destroy the ammunition of the cannon.