Distinguish steady and unsteady modes of ship power plant. As mentioned, the steady state is characterized by the constancy of the thermal state of the diesel engine parts. For transient modes of the diesel is characterized by instability of its technical and economic characteristics. In accordance with state standards distinguish the following basic modes of operation of diesel engines: nominal (full), maximum and minimum capacity, as well as treatment of minimally stable engine speed. Nominal mode (full) characterizes the effective power of long-term operation of diesel in rated crankshaft speed set by the manufacturer.

The value of the maximum allowable effective performance of diesel engines, which he can develop a limited time set manufacturer determines the maximum power mode. For marine diesel engines are not allowed to work more than 1 h with an overload of the power by 10%, and engine speeds – 3% above nominal. Long-term operation diesel at the lowest effective power, guaranteed by the manufacturer, describes the minimum power mode. The minimum effective capacity of 10-20% of the nominal, is determined to reduce the limit ship's speed. Mode of minimally stable engine speed marine diesel engine determines the maneuverability of the vessel. In this mode, the energy resources of diesel used by 3-4% rated power and 30% of the nominal speed of the crankshaft. The duration of the diesel in this mode should not exceed 2-3 h. In addition to the standard modes, marine diesel engines can also work on modes of 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. Plants that are shipping the device for separation of the propeller shaft diesel engines can operate and at idle speed. Diesel operation in this mode is accompanied by significant non-uniformity of the fuel, and sometimes pass outbreaks in the cylinders, leading to carbon formation on the pistons, seals rings, valves, spray nozzles, and therefore the duration of idling must not exceed 0.25-0.5 hours in exceptional cases, related to the preservation of people or cargo, the watch chief may decide to inclusion in the work and faulty diesel engines. This mode of operation is called EMS emergency. Sometimes in an emergency mode of operation of diesel engines is provided if necessary for the craft to the point 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 diesel engine.