 Turbo @-@ electric propulsion was selected for the battlecruisers despite the fact it needed more room than geared turbines to allow for better underwater protection that wartime experience showed was essential . First used in the New Mexico @-@ class battleships , it also had several other advantages . The turbines could run at their optimum speed , without regard to propeller speed , which was economical on fuel and the machinery could be easily sub @-@ divided which increased the ships ' ability to withstand torpedo hits . The substitution of flexible electric cables for bulky steam @-@ lines meant that the motors could be mounted further to the rear of the ship , which reduced both vibration and weight by shortening the propeller shafts . Also , the ship could go astern at full power simply by reversing the electrical polarity of the motors . Despite these factors and the fact that American companies would have struggled to produce the very large geared steam turbines needed for such big ships , the Curtis Company tried unsuccessfully to convince the Navy to reverse this decision . The Navy countered that doing so would mean a complete rearrangement of machinery spaces and a reduction in underwater protection . 
