COLREGS Rule 18: How Does a Power-Driven Vessel Interact with a Sailing Vessel? MCA Oral Exam Guide

Direct Answer to the COLREGS Rule 18 Exam Question

When a power-driven vessel underway in open water meets a sailing vessel on a reciprocal course, the power-driven vessel is the give-way vessel. Under Rule 18 (Responsibilities Between Vessels) of the International Regulations for Preventing Collisions at Sea (COLREGS), a power-driven vessel shall keep out of the way of a sailing vessel, and under Rule 16 she must take early and substantial action to keep well clear. Under Rule 8, that action should be large enough to be readily apparent to the other vessel and result in passing at a safe distance.

Why This Question is Critical for Your MCA Oral Exam

For any candidate sitting their OOW oral exam or Chief Mate assessment, a sound understanding of the responsibilities between vessels is essential. Examiners frame this question to test whether you know which rule applies, and when it doesn't.

The examiner is not just looking for a recitation of the rule. They want to see:

• Recognition of the other vessel's status.
• Understanding of the obligation to take early, positive action.
• Appreciation of the constraints of the sailing vessel.
• Communication of your intentions to the bridge team.

Understanding Rule 18

Rule 18 sets out the responsibilities between power-driven vessels, sailing vessels, vessels engaged in fishing, vessels restricted in their ability to manoeuvre (RAM), vessels not under command (NUC) and vessels constrained by their draught.

A sailing vessel (one under sail only, and not engaged in fishing) is a vessel you keep out of the way of. But Rule 18 opens with "Except where Rules 9, 10 and 13 otherwise require", so the duty is not absolute:

• Rule 13 (Overtaking): A sailing vessel overtaking you must keep out of your way.
• Rules 9 and 10 (Narrow Channels and TSS): A sailing vessel shall not impede the safe passage of a vessel that can safely navigate only within a narrow channel, or of a power-driven vessel following a traffic lane.

In open water with no other traffic, as in this question, it is straightforward: you give way.

Practical Application: What 'Early and Substantial' Means

If you are asked how you would carry out the manoeuvre, do not simply say 'alter course.' A professional response includes:

1. Early action: Do not wait until the last minute. On a reciprocal course, confirm the sailing vessel's aspect by radar and visual observation, and alter well in advance to remove any ambiguity.
2. Substantial action: A small alteration of 5 degrees may be missed by the sailing vessel. Make an alteration that is clearly apparent, typically 30 degrees or more, or reduce speed if that is more effective.
3. Well clear: Pass at a distance that leaves no risk of collision. Consider the wind and the sailing vessel's point of sailing, as she may need to tack or gybe.

Common Pitfalls for OOW Candidates

• Applying Rule 14 or Rule 15: The head-on and crossing rules apply only between two power-driven vessels. Between a power-driven vessel and a sailing vessel, Rule 18 decides who keeps clear (unless the sailing vessel is overtaking).
• Expecting the sailing vessel to move: Never suggest that because you are a large power-driven vessel, the sailing vessel should get out of your way in open water.
• Ignoring the Wind: A common follow-up question is, 'Does the wind direction matter?' It doesn't change your obligation, but knowing whether the yacht is beating, reaching or running helps you predict what she might do.
• Radar Bias: A small sailing vessel may give a poor radar echo, especially in sea clutter. Always keep a sharp visual lookout.

Exam Tips for Success

• Be Decisive: When the examiner asks what you would do, say: "Under Rule 18 I keep out of the way of the sailing vessel. I will take early and substantial action under Rule 16 to keep well clear."
• Situational Awareness: In real life there may be other vessels involved. Explain how you would deal with each under the rules.
• Bridge Resource Management (BRM): Mention that you would call the Master in line with the standing orders, and make sure the lookout and helmsman are aware of the manoeuvre.

Conclusion: Key Takeaways

Rule 18 is essential knowledge for any Officer of the Watch. The principle is the same whatever your certificate: in open water, the power-driven vessel keeps out of the way of a sailing vessel. Be ready to explain the 'what' (keep out of the way), the 'how' (early and substantial action) and the exceptions (overtaking, narrow channels and traffic lanes).

Updated 25 October 2026: clarified that Rules 14 and 15 don't apply between power-driven and sailing vessels, and added the Rule 9, 10 and 13 exceptions to Rule 18.