You should have had him fixed at about 3 months or so. I did that to mine (sorry Boom) and he's never sprayed. He goes through the motions, but he doesn't squirt. That being said, getting them fixed won't stop them from spraying. My ex-roommates cat didn't spray for 10 years. Until I moved in with my cat, then he started marking terratory.
I think it's too late now, you're going to have to deal with it....