How quickly a steam fleet can leave harbor

How long would the Home Fleet need to raise steam and leave harbor?

It depends on its ordered readiness state: a ship with a boiler lit might need about six hours, while units held at one or three hours' notice can depart much sooner.

Steam warships do not have one fixed harbor-to-sea time. A ship with one boiler operating might need roughly six hours to raise enough steam, while higher readiness states keep more boilers warm or running. An admiral can order ships held at three hours' notice, one hour's notice, or another defined condition according to the threat. Faster response therefore consumes fuel, labor, and machinery life before the fleet sails. Readiness is an operational choice that trades endurance and cost for reaction time.