Warspite's historical reconstruction replaced 24 old boilers with six Admiralty three-drum units, slightly raised power, sharply reduced fuel consumption, and saved about 1,500 tons. In the counterfactual calculation, four 850 psi boilers and matching turbines produce about 132,000 shaft horsepower, potentially enough to drive the hull near 28 knots. The additional machinery weight and space savings could then be assigned to protection or other improvements, turning the Queen Elizabeth class into a faster interim force before new battleships arrived. About 28 knots remains a practical hull-form ceiling, since every increment of power would not produce an unlimited increase in speed.
Chapter · 16:56-21:32
Warspite as the 850 psi test case
Replacing Warspite's historical six-boiler refit plant with four 850 psi boilers could plausibly yield a 28-knot Queen Elizabeth-class battleship and larger weight savings.