"Mallard" was fitted with twelve boilers during its 25-year career. These boilers were: 9024 (from construction), 8959 (from 4496 "Golden Shuttle", 13 June 1942), 8907 (from 2511 "Silver King", 1 August 1946), 8948 (from 31 "Golden Plover", "Walter K Whigham", 10 January 1951), 29301 (from 60019 "Bittern", 4 July 1952), 29315 (from 60014 "Silver Link", 23 April 1954), 29328 (new-build boiler, 7 June 1957), 29308 (from 60008 "Dwight D. Eisenhower", 27 August 1958), 29310 (from 60009 "Union of South Africa", 9 March 1960) and 27965 (from 60009 "Union of South Africa", 10 August 1961).