The ships were originally designed with propulsion machinery, but the Admiralty decided in 1917 to replace their four coal-fired boilers with more powerful oil-burning ones. This change could only be applied to the three least-advanced ships, including "Raleigh", although she was the only one who received the full upgrade. The ship was powered by four Brown-Curtis geared steam turbine sets, each driving one propeller shaft using steam provided by a dozen Yarrow boilers. The turbines were rated at for a speed of . When "Raleigh" ran her sea trials in 1920, she reached, but did not exceed, her designed speed. "Raleigh" carried enough fuel oil to give her a range of at .