The term power package refers to an electromechanical diesel engine (EMD) subassembly designed to be "easily" removed and replaced in order to restore engine performance lost due to wear or engine failure. Typical of heavy-duty internal combustion engines used in industrial applications, EMD engines are designed to allow cylinders, pistons, piston rings and connecting rods to be replaced in the overhaul without removing the entire engine assembly from its application location . This increases engine value, reduces downtime and allows the engine to be returned to true new engine performance. Other terms such as cylinder package, coating package, cylinder assembly and cylinder kit are used in the motor industry to describe similar assemblies. In the large engine industry, the term "power package" has also become generic and is often used to refer to assemblies used in non-EMD engines where "power pack" may be the preferred term, although both terms are functionally the same.
Due to the size and weight of the engine assembly and the difficulties to remove them and transport them for repair, they are usually repaired in situ in stationary applications and on the ship or locomotive in transport applications. The design of the engine for an "easy" service is done by necessity rather than by the desire to increase the service capacity of the engine. The power mounts are large and heavy and sufficient lifting equipment is required to lift the apparatus and assembly.