Jim says that "i had found an ally" in Ben Gunn. What did he mean by that and what did he hope could be a positive result for him and his friends. chapter 15

Ben Gunn is a marooned sailor Jim Hawkins finds on the island. He had been a part of Captain Flint's crew, like Long John Silver and Billy Bones. Ben does not respect the pirates. He was marooned on the island by them. He knows how these men operate and is a wealth of knowledge and strategy for Jim. Ben will allow Jim and his friends to formulate a plan of action.