Johannsen - male born 1830 Norway died 1882 Louisi

I am looking to find more information about my great great grandfather who emigrated from Norway. His death certificate from Louisiana says his name was John Johannsen, but I do not know that he was named John at birth in Norway. He was born about 1830 Norway and died in Louisiana on Aug. 23, 1882. Unfortunately I do not know what year he arrived in the USA, or even which port. I do not know who he married except for census records that say she was from Germany. I know a little more about his son, my great grandfather, John/Jurgen Johannsen who was born and lived his whole life in New Orleans, Louisiana, and married Emma Wiegel. I would really love to find out which part of Norway he was from! Thanks to anyone who might be related and has any information.