 Each propeller was 14 feet 9 inches ( 4 @.@ 50 m ) in diameter and each of the four propeller shafts was powered by two 22 @,@ 500 @-@ shaft @-@ horsepower ( 16 @,@ 800 kW ) electric motors acting in tandem . These motors were about five times the size of any earlier electric motor . Four General Electric turbo generators powered each propeller shaft and each was rated at 35 @,@ 200 kilowatts ( 47 @,@ 200 hp ) , 5000 volts and 4620 amps of direct current ( DC ) . Each of the four AC alternators produced 40 @,@ 000 KVA . Sixteen water @-@ tube boilers , each in their own individual compartment , provided steam for the generators at a working pressure of 295 psi ( 2 @,@ 034 kPa ; 21 kgf / cm2 ) and a temperature of 460 ° F ( 238 ° C ) . The turbo @-@ electric machinery of the Lexington @-@ class ships was designed to produce a total of 180 @,@ 000 shaft horsepower ( 130 @,@ 000 kW ) and propel the ships at 33 @.@ 25 knots ( 61 @.@ 58 km / h ; 38 @.@ 26 mph ) , but each ship reached over 202 @,@ 000 shp ( 151 @,@ 000 kW ) and 34 @.@ 5 knots ( 63 @.@ 9 km / h ; 39 @.@ 7 mph ) during sea trials in 1928 . Six 750 @-@ kilowatt ( 1 @,@ 010 hp ) DC turbo generators were installed in the upper levels of the two main turbine compartments . 
