A great research work is The Wooden World: An Anatomy of the Georgian Navy, by N.A.M. Rodger. Keep in mind that Rodger specifically writes about the mid-to-late 1700s, and while he focuses on the Royal Navy, there are plenty of accounts relating to the merchant marine as well (especially since most of the RN's sailors would have sailed as civilian merchant sailors during peacetime).

Off the top of my head, a firsthand account from a merchant sailor is Richard Henry Dana's Two Years Before the Mast.