When intending to overtake a vessel in a narrow channel on the port side, how should you signal your intentions?

When intending to overtake a vessel in a narrow channel on the port side, signaling with two prolonged blasts followed by two short blasts is the correct procedure. This signal communicates your intention to overtake to the other vessel in a clear and unmistakable manner. Specifically, this combination of sounds is recognized under the International Regulations for Preventing Collisions at Sea (COLREGs), which govern maritime right-of-way and navigation signaling.

Using two prolonged blasts followed by two short blasts indicates that you intend to pass the other vessel on its port side. It is essential to provide this signal well in advance of your maneuver to allow the other vessel to understand your intentions and maintain safety in the narrow channel. Clear signaling helps to prevent misunderstandings that could lead to dangerous situations, especially in confined waters where navigation is more challenging.

The other signals listed would not effectively communicate the intention to overtake in this context. For instance, a single prolonged blast typically indicates your intention to depart or a warning, while three short blasts may indicate that you are reversing or maneuvering in a specific way. One short blast also does not convey the specific intent to overtake on the port side, as it is generally used to signal that you intend to pass on the starboard side.