A lot of great recommendations so far. A book I recommend to so many people young and old is the book Dove by Robin Lee Graham. Probably one of the greatest adventure/coming of age books ever written, by a young kid who sails around the world alone in a small boat. I believe it's plenty age appropriate for a boy the age of yours, there's some mention of drinking briefly and there's a bit of a romance aspect to the book, but he deliberately made the book pretty PG in all respects.
Reading this book was a major formative experience for me as a young kid and a lot of men I've given it to have felt the same way. It set me on a path to my first career working at sea and ironically the first foreign port of call ever made was the same as the author of this book in Suva, Fiji.
The book speaks to that desire in all of us to not just pursue but follow through on what we feel called to, even if society deems it a wild and hapless pursuit. In today's world I think a lot of boys need to be exposed to this message more than ever. It's a quick read, read it yourself and see if you think it's a good one for your son. I guarantee you'll both thoroughly enjoy it.