Thank you for nice words! With such a recommandation the samaritan has got to make a try!
I do this online, tracing names in the online censuses, making a lot of guesses about how names and places were spelled. (- much more fun than puzzles og cross-words)
This one is difficult to do solve online, because he probably is born after the 1865 census, and emmigrates before the 1900 census. The only help is the emmigrant lists of Kristiansand port.
The best candidate there is Severin Olsen, born 1867, from Mandal, who emmigrates in 1883, an unmarried sailor.
Another possible candidate is Søren Olsen, also born 1867, from Mandal, who emmigrates in 1892, heading for Philadelphia. He is a coachman's boy.
There is no bygdebok for Mandal town. One way to do further research is to do lookup in the church records at Statsarkivet in Kristiansand. - If you not are able to get any more information about parents or other relatives.