If i didn't go to Marine boot camp 4 years ago would i still be able to join now?

The Marine Corps, unlike other branches of the military, has a long and unforgiving memory. If you attempted to enlist four years ago and at the last minute changed your mind, they haven't forgotten it. It's in the record, whether you remind them of it or not. This time around, if you qualify physically, mentally, morally, and age wise, they will probably keep a sharp eye and mind on you. Good Luck.