Sorry for the delay in getting back to you. If you go to my research pages at:
You'll find the address for the National Military Personnel Records Center. try writing them (SF Form 80s are on the webpage to download) with as much info as possible. If you know the name of the ship, check if they have an association webpage. Also contact the national Archives, and the US Navy History Center. There are several associations of underage sailors, that could probably help you as well.