Renown's historical modernization replaced 42 boilers with eight and raised output from about 112,000 to 120,000 shaft horsepower, but added weight reduced her speed. Four 850 psi boilers could instead provide roughly 132,000 shaft horsepower while saving still more machinery weight and volume. Designers might use that margin to retain about 32 knots, limit the rise in deep-load displacement, or strengthen belt and deck protection. A propulsion advance changes the whole weight budget, leaving designers to divide the benefit between speed, displacement, and protection.
Notable Point · 48:13-50:22
Renown trades machinery weight between speed and protection
Four 850 psi boilers could give Renown more power than her historical eight-boiler reconstruction while letting designers preserve speed or deepen protection.