The study of a ship’s machinery installation and her propulsionPropulsion plant, namely, of the main machinerymain machinery (prime mover) and auxiliary enginesEngines, auxiliary, of the propellerPropeller and the required rudderRudder, is subject of specialized literature, a sample of which is cited in the given list of references. In the context of the present book, we will limit ourselves to some general comments on the selection criteria, including the influence of recent regulatory and market developments, and outline the recommended procedure regarding the selection of the machinery installation, the propulsive and steeringSteering devices as to meet the needs of the preliminary designPreliminary design of a ship.