Navigation rules - page 5
3.5 Rule 13
The Rule - Overtaking
(a) Notwithstanding anything contained in Rules 4 through 18, any vessel overtaking any other shall keep out of the way of the vessel being overtaken.
(b) A vessel shall be deemed to be overtaking when coming up with another vessel from a direction more than 22.5 degrees abaft her beam; that is, in such a position with reference to the vessel she is overtaking, that at night she would be able to see only the sternlight of that vessel but neither of her sidelights.
(c) When a vessel is in any doubt as to whether she is overtaking another, she shall assume that this is the case and act accordingly.
(d) Any subsequent alteration of the bearing between the two vessels shall not make the overtaking vessel a crossing vessel within the meaning of these Rules or relieve her of the duty of keeping clear of the overtaken vessel until she is finally past and clear.
Examples: Sailboat is overtaking a powerboat
The sailboat is overtaking a powerboat. Any vessel overtaking another must Give Way, therefore the sailboat must Give Way. This is also the case if the powerboat was lying adrift in this position.
Examples: Sailboat adrift powerboat
The adrift powerboat must Give Way to the sailboat. The reason for this is that adrift is actually considered as "underway" even with engines off. Often times in lakes or sheltered bays we will encounter powerboats that are adrift as such sunbathing etc. The rules are clear - adrift is underway and appropriate Giving Way must be done. However, the rules are also clear in that you must avoid collision.