Complex sentence: Two water-tube boilers with a combined heating surface of supplied steam at 400 lb f/in 2 to a turbo generator, which fed current to a propulsion motor on her propeller shaft.
Split into simpler sentences: Two water-tube boilers with a combined heating surface of. They supplied steam at 400 lb f/in 2 to a turbo generator that fed current to a propulsion motor on her propeller shaft.