Abstract: The multi-engine consists in one embodiment of a relatively large turbocharged ship's diesel engine and three smaller turbocharged auxiliary or stand-by diesel engines. The main engine is primarily adapted for propelling the ship while the auxiliary engines solely drive electric generators. In view of the rigorous demands on the security of the delivery of electricity it is desirable to operate one or more of the auxiliary engines in stand-by mode during a substantial part of the operation time of the plant, i.e. unloaded or at low load. This involves problems for the engine concerned because the charging air pressure generated by the associated turbocharger is then lower than the exhaust gas pressure.