Try the following:

1) go to http://www.dejanews.com and do a POWER SEARCH for [ sea songs & shanties ] .. set AGE to OLD/50 or more

2) go to http://www.dogpile.com and search for same thing as above.

3) go to dogpile/search: [ sea songs & shanties | american shipping ]

may take you a month or two to read all of it

-Gene