I don't know if this will help but there is a Terje Rinnan on the Social Security Death index born 24 Dec 1914 died July 1985 Last residence New Orleans. Also there is a Julius Rinan born in 1898 could this be Carl Julius? http://ssdi.genealogy.rootsweb.com/cgi-bin/ssdi.cgi Carla
Maybe you are related to the famous Captain Arne Rinnan, who rescued 438 persons off Christmas Islands. He is from the Trøndelag area, and I should guess that his name originates from the Rinnan farm near Levanger in North-Trøndelag. Actually, some of my ancestors came from that farm too. As to the question about Terje Rinnan's career at sea, it should be possible to trace him in the seaman's registers. However, he will only be listed there as long as he was considered a Norwegian citizen. At the Statsarkivet in Trondheim they have an old card archive sorted by last name, and you could try writing them and ask if they will look him up.
Address: Statsarkivet i Trondheim Postboks 2825 Elgesæter 7432 Trondheim
Don't expect too much, as they usually do not have the cappasiti to spend a lot of time on lookups. If you have no luck, I will see what I can do the next time i visit the archives.