Complex sentence: During fitting out she was damaged amidships by Donaldson South American Line's 7,131 ton cargo ship which was trying to dock in poor visibility, but by 17 February "Viceroy of India" was ready for sea trials, on which she averaged.
Split into simpler sentences: During fitting out she was damaged amidships by Donaldson South American Line's cargo ship, which was trying to dock in poor visibility. However by 17 February "Viceroy of India" was ready for sea trials, on which she averaged.