The Queen Elizabeths generated about 75,000 shaft horsepower from 24 water-tube boilers, compared with the Lion class's roughly 70,000 from 42 boilers. Eighteen newer boilers produced about 90,000 shaft horsepower in the Courageous class, showing how quickly machinery output advanced around the same period. That improvement was substantial, but the heavier battleship hull remained shorter than the battlecruiser hull used for comparison. A 28-knot design would likely have required another 10 to 15 metres of length and additional small-tube Yarrow boilers, increasing both capability and design risk.
Notable Point · 18:22-22:04
Boiler count, power, and the missing hull length
A comparison with the Lion and Courageous classes shows how machinery improved rapidly, but a truly faster Queen Elizabeth would have needed a longer hull and more advanced boilers.