My great grandfather is Carl Marius Julius Daehne and my grandmother had said that he was a Jansen, not a Daehne. His blood father, Jansen was a sea captain, however, I don't believe that we have a first name and based on your message, it appears that both are named Julius. What I do know about him is that he was a sea captain and his ship went down at Cape Horn in a storm (not aware of survivors). I have some info, but need to look over my files.
Please feel free to contact me.