What is the duty of a vessel under Rule 20 regarding engine operation?

The duty of a vessel under Rule 20 emphasizes the importance of operating engines responsibly according to safe navigation principles. Rule 20 is part of the COLREGs that governs conduct in various visibility conditions and highlights the need for vessels to navigate safely to prevent collisions. This means that regardless of the visibility or conditions, the vessel's operator must ensure that the vessel is managed in a manner that prioritizes safe navigation practices.

This encompasses maintaining a proper lookout, travelling at a safe speed, and being prepared to take immediate action if necessary. By focusing on responsible engine operation in line with safe navigation principles, the operator can adjust the vessel's speed, course, and engine power as required to ensure safety and compliance with the regulations.

The other options do not fully encapsulate the broader responsibility dictated by Rule 20. For instance, while technical specifications and clear visibility are important considerations in operations, they are too narrow to cover the overall duty to navigate safely under varying circumstances. Operating at maximum speed contradicts safe navigation principles since it could lead to a greater risk of collisions, especially in congested or reduced visibility conditions. Thus, the emphasis on responsible operation according to safe navigation principles aligns perfectly with the intent of Rule 20.