Hi---I appreciate you requesting me! The best way to get this boy to trust humans is to do 2 things - first, borrow a Have a Heart trap from Animal Control or a Rescue group, trap hm and have him neutered. If you don't feel comfortable keeping him indoors, the 'tried and true' method of getting a cat to trust is to use a teaser toy of some type - feather teaser or laser pointer. Sit on the deck with him and see if you can get him to interact with you and the toys.
It can take quite a while - several weeks before he feels secure enough with you to trust you. Just be patient. Unless he has had terrible experiences with humans, or is an older boy that just can't change, you should be able to rehabilitate him. Keeping him indoors (after neutering) of course, is the most effective way of changing him (put him in a fairly small room where he doesn't feel overwhelmed). Use the same toys and techniques of quiely talking with him and making him feel secure, and you should se major signs of success.
Please let me know if I can help further and how things go.