Did any naval ships share Queen Mary's power plant, and why weren't variations of it used?
Short answerThe machinery evolved from Princess Royal to Queen Mary and then Tiger, with variations appearing through successive designs.
NotesPrincess Royal's power plant precedes Queen Mary's, which in turn leads into Tiger's. The machinery evolved through those successive designs. Parsons and Brown-Curtis machinery competed to provide comparable power and performance, with one sometimes doing better than the other. Warspite supplies another example, combining Yarrow boilers with Parsons turbines.