It's certainly been quite a while since it was played in concert. I think it was eclipsed by the more popular Wreck of the Edmund Fitzgerald. I can't find it listed in any of the concert summaries at Wayne Francis' Lightfoot website even going back as far as 1995. Being that it was a topical song of a certain time period and never charted like "Wreck" did, it was probably rotated out of his repertoire. It's a very moving song though and I pop in my Sunday Concert CD and play it every now and then.
Minor correction: The song title is actually Ballad of the Yarmouth Castle, as taken from the album cover (yes, I still have my original well worn vinyl LP as well as a CD version of Sunday Concert). There actually is a Yarmouth Castle, built by Henry VIII on the Isle of Wight,
http://www.guide-to-castles-of-europ...th-castle.html however, Lightfoot's song deals with the sinking of a ship.