Power-driven vessel versus sailing vessel

In the normal Rule 18 situation, a power-driven vessel underway keeps out of the way of a sailing vessel.

But this is not absolute.

A sailing vessel may still have to keep clear under:

Rule 9, narrow channels

Rule 10, traffic separation schemes

Rule 13, overtaking

other special circumstances

A vessel using sails while its machinery is also propelling it is treated as a power-driven vessel for the Rules.