Looking for Great Grandfather Erickson of Texas

My grandfather, Ferdinand Louis Erickson born November 25, 1898, spent his adult life trying to locate his biological father. As an infant he lived in Galveston, TX under a different surname. In the early 1900's he decided to join the Navy and it was then he learned his mother had remarried and he had been raised under his step-father's name. His mother told him that she was informed his biological father had been killed when he was an infant, she remarried and several years later first husband Erickson returned home. When he discovered she had remarried and had born several children with the 2nd husband, he left the area and his whereabouts from then on has been a mystery. The only ID clue I have is that my great-grandfather may have been known as Carl or Karl and he may have been in the Merchant Marines. If anyone has any information to help me ID my great-grandfather on my mother's side of the family I would be very grateful.