I would point out that JFK would not have had too much time to do a major refit to the Presidential Yacht during his time in office. He only renamed it. . . I very much doubt he would have had even the bell replaced. That would have been odd. This yacht was refitted first for Franklin D. Roosevelt in the 1930s from a WWI mine sweeper.
I saw it being restored from an almost total wreck about ten years ago after it was found IIRC in Sausalito, half-sunk, and rotting away. It was towed to Stockton to be rebuilt and restored to the 1930s floating palace of the Roosevelt era.
I get that. But whether or not JFK was around for it or not. Having that inscription on a boat he once used would be the key. But like I said I did not see an inscription on the bell. Camelot was total bs as well. Just saying.