Well, now that I had found the boat, you would have thought I had had enough of truantry for once, but in the meantime I had taken another notion and become so obstinately fond of it that I would have carried it out, I believe, in the teeth of Captain Smollett himself. This was to slip out under cover of the night, cut the Hispaniola adrift, and let her go ashore where she fancied. I had quite made up my mind that the mutineers, after their repulse of the morning, had nothing nearer their hearts than to up anchor and away to sea; this, I thought, it would be a fine thing to prevent, and now that I had seen how they left their watchmen unprovided with a boat, I thought it might be done with little risk. (22.35)
These guerilla actions against the pirates seem to come completely out of the blue. Sure, Jim says he "thought it would be a fine thing to prevent" the mutineers from escaping, but it's quite a jump from that to rowing out to the boat and setting it adrift. Do we see any signs that Jim is learning how to fight pirates from experience, or is he just naturally gifted at waging war against a small band of bloodthirsty criminals?