The Command Question: Who Decides the Engineering Watch Arrangement?
As Master, you set the engineering watch arrangement. MSN 1858 (the MCA's watchkeeping standard for yachts) frames this as a command judgment, not a default. You must match the arrangement to the risk — at sea, at anchor, and in port — and you must be able to justify it.
Three Terms the Examiner Will Probe
Unmanned Machinery Space (UMS): The machinery space operates without a watchkeeper continuously present. Automated alarms and safety systems substitute for continuous attendance. This is not the same as an unmonitored space — the systems must be fit for purpose and the response arrangements must be defined and understood by the crew.
Continuous machinery watch: A competent engineer is present in the machinery space at all times. Required where UMS standards cannot be met, or where the Master judges the risk demands it — port arrival/departure, adverse weather, degraded plant, unfamiliar crew.
Engineering officer on call (OOC): Used in conjunction with UMS. The engineer is available to respond to alarms but is not continuously present. The Master must be satisfied that alarm response times and escalation procedures are appropriate for the vessel's situation.
The examiner will test whether you know that UMS is a standard to be achieved and maintained, not a standing permission that removes your responsibility.
The Command Decision at Sea
Your default arrangement should be documented in the SMS. Where UMS is approved and the plant is operating normally, OOC may be appropriate. But as Master you must reassess continuously: high sea states, restricted channels, manoeuvring, a defective alarm system, or a recently joined engineer officer — any of these may require you to reinstate a continuous watch. This is a command call, and the oral examiner expects you to own it.
At Anchor
Do not treat anchor watch as a reduced-risk state. Holding ground, dragging, a single anchor, weather deterioration, and the potential need for immediate departure all affect the engineering readiness you require. Manoeuvring machinery should be available at a notice period you have consciously set and communicated. If you need engines at 30 minutes' notice, your engineering watch arrangement must deliver that.
In Port
The temptation is to stand down engineering watch entirely. The command standard requires you to consider: shore power reliability, fire risk from hot work or cargo operations, emergency departure requirements, and crew fatigue. Essential services — fire pumps, bilge systems, emergency generator — must remain available. A nominated responsible person, even if not a full watch, may be necessary.
The Connecting Principle
All three states require the same mental process: identify the hazard profile, set the watch arrangement to match it, communicate it clearly, and document it where the SMS requires. MSN 1858 gives you the framework; the oral examiner is testing whether you apply it as a Master, not as a watchkeeper.