When it is under sail, not in a narrow channel or fairway and NOT overtaking.
Please refer to Rules 12-18 in the link provided below.
When it is being overtaken
only when under sail alone and crossing the path of the powerboat
only when under sail alone and is crossing path of powerboat
The question should be "When is the sailboat the stand-on vessel...? The answer is if the sailboat has an engine and if it is in operation, the sailboat is treated as a power boat in determining stand-on status. The right-of-way would then follow the rules for power boats.
power boat
When a sail boat overtakes a power boat the power boat is the stand on vessel.
When a sailboat overtakes a powerboat, the powerboat is the stand-on vessel. (Ref: SB-29)
Powerboat
power boat
When a power-driven vessel is being overtaken by a sailboat, the power-driven vessel is considered the "stand-on" vessel, meaning it must maintain its course and speed. The sailboat, as the "give-way" vessel, is required to take action to avoid a collision. The sailboat should ensure it passes safely and can alter its course if necessary to avoid the power-driven vessel. It's crucial for both vessels to be aware of their responsibilities to ensure safe navigation.
When a sailboat overtakes a powerboat, the powerboat is the stand-on vessel. (Ref: SB-29)
When a sailboat overtakes a powerboat, the powerboat is the stand-on vessel. (Ref: SB-29)