Here's what I found. These Morgan's and Chapman's may not be your family tho - there are so many people out there with the same name! I found a Clark W. Morgan, Thomas W. Morgan, Junius S. Morgan, and an Ebeneazer Morgan - he was a Capt. who sailed from New London, CT in 1864. I don't know anything about the others but they may be a place to start looking as your Morgan may be related somehow. The seaman seemed to run in certain families I'm learning. I found a Schooner The William H. Rowe that had a Master named Morgan but no first name listed - this was out of Rondout, NY in 1872. A ship called Fannie & Edith out of Portsmouth, NH had a Master named Chapman - again - no first name listed. And the Schooner William had a William Chapman on it. This info was found at www.essex-family-history-co.uk/shipwreck.htm
The other info came from books I have here -
Have you checked The Seaman's Protection Certificate site?
Some seaman had this certificate and other didn't. I had no luck looking for my own missing seaman there. It's worth a try tho. I'll keep your e-mail in case I turn up anything else. Also, in your own searches keep an eye out for an Asby, Espy, Espie, Espey or something similiar - he's my missing seaman - left Philadelphia in 1816 and apparently never returned. Hope I was a tiny bit helpful. Oh, yes, have you tried the Mystic Seaport site? They have a lot of east coast info -