Candidates consistently reduce this topic to 'start the engine and check the gauges.' Examiners want command-level thinking: you are responsible for a system you may not physically operate yourself — know what must work, what must be monitored, what must be recorded, and what you do when it fails.
The trap: treating plant operation as crew-level, not command-level
At command standard you must be able to describe the operational principles of the main propulsion plant and its auxiliaries, recognise symptoms of impending failure, and articulate the management decisions that follow. You do not need engineer-level depth, but you must not be vague.
Main propulsion — pre-departure readiness
Before departure confirm:
- Cooling water (raw water strainer clear, impeller service history known, sea cock open)
- Lubricating oil level and pressure at start — know your normal operating range; investigate any deviation immediately
- Fuel system: adequate quantity, correct grade, filter differential pressure within limits, water separator drained
- Engine room bilge: dry or at known normal level; any increase demands investigation before sailing
- All alarms and shutdowns functional (test where practicable)
- Belt tension and condition on all drive systems (alternators, raw water pump on some installations)
Auxiliaries — what the examiner expects you to manage
Generators: load-sharing logic on twin-generator vessels, transfer procedures without interrupting essential services. Know which services are on the emergency switchboard.
Emergency generator: auto-start tested regularly; fuel level and type (flash point ≥43 °C permitted for emergency generators, versus ≥60 °C for main plant under SOLAS II-2 Reg 4). Know which essential services it supports — navigation lights, GMDSS, steering alarms.
Steering gear: tested within 12 hours before departure; emergency steering drill at least every three months including direct control from the steering gear compartment — this is your responsibility to arrange, record and sign off.
Bilge systems: know your bilge pump capacities and activation logic. A high bilge alarm is a command decision, not just an engineering matter.
Fuel transfer: risk of overflow to bilge or overboard — maintain an Annex I record, ensure valves are positioned correctly before and after transfer, person stationed at the vent.
Monitoring and records
Engine room log entries should record temperatures, pressures and running hours at meaningful intervals. Trends matter: a rising coolant temperature over successive passages is a management signal, not a one-watch problem.
When things go wrong — command response
Low oil pressure: immediate engine stop or load reduction — never 'watch and wait.' High coolant temperature: isolate load, check raw water flow first, then freshwater circuit. Loss of propulsion underway: anchor if water permits, broadcast SECURITÉ or MAYDAY as appropriate, advise owner/manager per your SMS procedures.