Isle of Swords by Wayne Thomas Batson
Declan Ross, the pirate captain of the William Wallace, has a problem-several, actually. Ross doesn't want to be a pirate any more, but he doesn't have enough money to buy a house. Plus his daughter, Anne wants to become a real pirate herself.
Anne finds a young man unconscious in the sand on an island. When he wakes up, he can't remember anything. Monks from an island that was once a safe haven for pirates ask Captain Ross to find the legendary treasure on the Isle of Swords. Will the crew abord the William Wallace find the treasure before the other pirates do? Will Ross Give up the treasure that could free him from being a pirate forever? And who will the mysterious young man turn out to be?