 The Lion @-@ class ships had two paired sets of Parsons direct @-@ drive steam turbines , each of which was housed in a separate engine @-@ room . The wing shafts were coupled to high @-@ pressure turbines and these exhausted into low @-@ pressure turbines which drove the inner shafts . A cruising stage was built into the casing of each high @-@ pressure ahead turbine . Their three @-@ bladed propellers were 12 feet 3 inches ( 3 @.@ 73 m ) in diameter on the inner shafts while the outer propellers were 11 feet 8 inches ( 3 @.@ 56 m ) in diameter . The turbines were powered by forty @-@ two Yarrow water @-@ tube boilers in seven boiler rooms . They were designed to produce a total of 70 @,@ 000 shaft horsepower ( 52 @,@ 199 kW ) , but achieved more than 76 @,@ 000 shp ( 56 @,@ 673 kW ) during trials , although Lion did not exceed her designed speed of 28 knots ( 52 km / h ; 32 mph ) and Princess Royal only reached 28 @.@ 5 knots . 
