Engine room

On a ship, the engine room (ER)^[1] is the compartment where the machinery for marine propulsion is located. The engine room is generally the largest physical compartment of the machinery space. It houses the vessel's prime mover, usually some variations of a heat engine (steam engine, diesel engine, gas or steam turbine). On some ships, there may be more than one engine room, such as forward and aft, or port or starboard engine rooms, or may be simply numbered. To increase a vessel's safety and chances of surviving damage, the machinery necessary for the ship's operation may be segregated into various spaces.

The engine room is usually located near the bottom, at the rear or aft end of the vessel, and comprises few compartments. This design maximizes the cargo carrying capacity of the vessel and situates the prime mover close to the propeller, minimizing equipment cost and problems posed from long shaft lines. On some ships, the engine room may be situated mid-ship, such as on vessels built from 1900 to the 1960s, or forward and even high, such as on diesel-electric vessels.