PF: The true story! - It wasn't a puffer! TS Queen Mary
was a steamer launched in 1933 and worked on the Clyde. In 1935, Williamson-Buchanan, her owners, were contacted by the Cunard Company which was getting ready to have its new liner launched by Her Majesty Queen Mary – so Cunard reached agreement with Williamson-Buchanan that the turbine steamer would become TS Queen Mary II, and presented a portrait of Her Majesty to hang in the forward lounge of the Clyde steamer, while their liner became the RMS Queen Mary
Stories about changing ship names is a very old superstition that has no meaning at all. Modern ships change owners and names regularly. I owned many small boats and changed the names of most of them to suit myself.