Conrad Ernest Gardner 1856-?

[Flis]

This is a bit of a long shot but my great great uncle, Conrad Ernest Gardner jumped ship (HMS Peterel) in Mexico in March 1875.  The family story was that he died in a seaman's home in New York.  I have no information about him since that date but do have a picture of him taken by a New Orleans photographer in which he looks rather older than the 19 years he would have been when he ran.  Has anyone any ideas as to how I could find out what happened to him?
Thanks
Felicity