 To save design time, the four-shaft unit machinery from the Lion-class battleship was duplicated with alternating boiler and engine rooms. Vanguard had four sets of single-reduction geared Parsons steam turbines housed in separate engine rooms. Each set consisted of one high-pressure and one low-pressure turbine, driving a propeller that was 14 feet 9 inches (4.5 m) in diameter. The turbines were powered by eight Admiralty 3-drum boilers in four boiler rooms at a working pressure of 350 psi (2,413 kPa; 25 kgf / cm2) and temperature of 700°F (371°C). The engines were designed to produce a total of 130,000 shaft horsepower (97,000 kW) and a speed of 30 knots (56 km / h; 35 mph), but achieved more than 136,000 shp (101,000 kW) during the ship's sea trials in July 1946, when she reached a speed of 31.57 knots (58.47 km / h; 36.33 mph). After trials, the three-bladed propellers on the inboard shafts were replaced by five-bladed propellers in an unsuccessful attempt to reduce vibrations of the inboard propeller shafts.
