Oliver Hansen Depart Bergen 1859-60

My great grandfather supposedly left Bergen in 1859-60 at the age of 15 to learn to be a sailor. I have not been able to find any records of his birth or family, and unfortunately know very little about his Norwegian background. The info I have is as follows: He was supposedly born in April of 1847, although we think this could have been 1845. I do not know his parents names or his place of birth other than the Bergen area. His mother died when he was 12 years old, and he was the oldest of six children. He was sent to sea by his father to learn the trade of seaman. Oliver was not happy about this and jumped ship somewhere in the Atlantic and stowed away aboard a freighter and came to America. We have no idea where he came into the USA, but he ended up in Baltimore, Md. where he spent the rest of his life. Upon entering the USA he supposedly changed the spelling of his last name from "Hanson" to "Hansen". I am also questioning his first name of Oliver, which I have no idea of this was his real given name or if it was changed from Ole Ivar, or something else to Oliver. I have been searching for years to find a record of his brithplace, parents names, or sibling names with no luck. There has to be a record somewhere of a boy who went to sea and jumped ship never to return to Norway, but I have no idea how to research this. Any help is greatly appreciated.