Distinguish between steady and unsteady modes of ship power plant. As mentioned, set the mode characterized by the constancy of the thermal state of engine parts. For unsteady modes of engine characteristic instability of its techno-economic characteristics. In accordance with state standards differ in the following basic modes of operation of diesel engines: the nominal (full), and maximum minimum power and the regime of minimum sustained speeds of crankshaft. Nominal mode (complete) the effective power characterizes long-term work of diesel at rated speed crankshaft installed by the manufacturer. The value of the maximum allowable effective performance of diesel engines, which he can develop a limited time set by the manufacturer determines the mode of maximum power. For marine diesel engines allowed to work no more than 1 h with an overload of power at 10%, and the frequency of rotation of the crankshaft – at 3% above nominal. Long-term operation of diesel at the lowest effective power, guaranteed by the manufacturer, describes the mode of minimum power.

Minimum effective capacity is 10-20% of the nominal, the limit is determined by reducing the speed of the vessel. Mode minimally stable frequency of crankshaft rotation of a marine diesel engine determines the possibility of maneuvering the vessel. On this mode the energy resources of diesel used by 3-4% of rated capacity and 30% rated speed of crankshaft. Duration of diesel in this mode should not exceed 2-3 h. In addition to the standard modes, marine diesel engines can also work on modes operating power and idling.

By operating power include high power diesel engine for the planned load and speed of the vessel. For cargo ships, it is 85 – 90% of rated capacity for towing – 90-95%. In determining the targets of the ship on the operational performance of diesel fuel consumption is normalized. Installation of vessels device for separation of diesel engines from the propeller shaft, can also work on mode idling. Diesel operation in this mode is accompanied by considerable unevenness of the fuel, and sometimes pass outbreaks in the cylinders, resulting in carbon formation on the pistons, sealing rings, valves, spray nozzles, so the duration of the idle mode should not exceed 0,25-0,5 hours in exceptional cases related to the rescue of people or cargo, the watch chief may decide to inclusion in the work and faulty diesel engines. This mode of operation of ems emergency call. Sometimes in an emergency mode of operation of diesel engines is provided if required the vessel to move to a place of repair. In this case, the watch chief (mechanic) must be organized under constant watch in the engine room to closely monitor the technical condition of the engine.