When two power driven vessels are approaching head-on or nearly so, either vessel shall indicate its intent which the other vessel shall answer promptly. In a meeting situation, neither vessel is the stand-on vessel.
It is generally accepted that you should alter course to starboard and pass port-to-port. The accompanying sound signal is one short blast.
If you cannot pass port-to-port due to an obstruction or other vessels, you should sound two short blasts to indicate your intention to pass starboard-to-starboard. Make sure the other vessel understands your intent before proceeding. The other vessel should return your two-short-blast signal.
When two vessels are moving in the same direction, and the astern vessel wishes to pass, it must initiate the signal to pass as shown in the diagram. The vessel passing is the give-way vessel and should keep out of the way of the vessel being passed. The vessel being passed is the stand-on vessel and must maintain its course and speed. If the stand-on vessel realizes that the course intended by the give-way vessel is not safe, it should sound the danger or doubt signal.
A vessel is deemed to be overtaking when the vessel is approaching the vessel ahead in a direction of 22.5 degrees abaft her beam. At night you would only be able to see the stern light of the vessel being overtaken. You would not be able to see either sidelight.
If you are overtaking a vessel, remember that you are the give-way vessel until well past, and safely clear of, the passed vessel. Do not cut in front of, impede or endanger another vessel.
"I intend to pass you on your port side" - 2 short blasts (1 sec.)
"Agreement" - 2 short blasts (1 sec.)
"I intend to pass you on your starboard side" - 1 short blast (1 sec.)
"Agreement" - 1 short blast (1 sec.)
If the sailboat is overtaking a powerboat, the powerboat is the stand-on vessel and the sailboat must give way.