Why did Jim risk leaving the stockade? How did his plans change?

Bored and scared of the blood and bodies, Jim decides to leave the compound to look for Gunn's boat, although the knows that it is against the wishes of his comrades. As he sneaks to the anchorage, he sees Long John Silver in a smaller boat beside the larger Hispanolia, speaking to two pirates who are onboard. Suddenly, Silver departs and the two men on board go down to the cabin.

Jim finds the handmade boat under a tent and near a white rock. Interestingly, the boat is small and light, portable, and is a wood framework covered with goatskin - Jim calls the boat a coracle. Deciding that the pirates will soon take the anchor up and wanting to stop them, Jim decides to cut the Hispanolia loose and merely let it land anywhere the wind and current take it, thereby stopping the pirates. By this time, the night is dark and the only visible things on the horizon are the light in the ships cabin and a great fire in the swamp, where the pirates are drinking. In these conditions, Jim sets out in the coracle.