Pederast or ebeophile (the spelling of the last I'm not sure about). Pedophile is an adult attracted to pre-pubescent children, the other two are men attracted to adolescents, which would include underage teenaged boys.
Which is often SOP for homosexuals and has been throughout history.
Strictly speaking, a pedophile is attracted to prepubescent boys; a pederast is attracted to adolescent boys; an ephebophile is attracted to young men (17-21).