What maneuvering sound signal would a power driven vessel should give to the another vessel when they are in sight with one another to alter course to starboard?

(a) When vessels are in sightVessels shall be deemed to be in sight of one another only when one can be observed visually from the other. of one another, a power-driven vesselThe term 'power-driven vessel' means any vessel propelled by machinery. underwayThe word 'underway' means that a vessel is not at anchor, or made fast to the shore, or aground. , when manoeuvring as authorized or required by these Rules, shall indicate that manoeuvre by the following signals on her whistle

– one short blastThe term 'short blast' means a blast of about one second's duration.Â to mean ‘I am altering my course to starboard ‘;

– two short blasts to mean ‘I am altering my course to port ‘;

– three short blasts to mean ‘I am operating astern propulsion’.

(b) Any vesselThe word 'vessel includes every description of water craft, including non-displacement craft, WIG craft and seaplanes, used or capable of being used as a means of transportation on water'. may supplement the whistle signals prescribed in paragraph (a) of this Rule by light signals, repeated as appropriate, whilst the manoeuvre is being carried out:

(i) these light signals shall have the following significance:

– one flash to mean ‘I am altering my course to starboard ‘;

– two flashes to mean ‘I am altering my course to port ‘;

– three flashes to mean ‘I am operating astern propulsion’;

(ii) the duration of each flash shall be about one second, the interval between flashes shall be about one second, and the interval between successive signals shall be not less than ten seconds;

(iii) the light used for this signals shall, if fitted, be an all-round white light, visible at a minimum range of 5 miles and shall comply with the provisions of Annex I to these Regulations.

(c) When in sight of one another in a narrow channel or fairwayA fairway means an open area of navigable water that is often maintained by an authority i.e a port or harbour.:

(i) a vessel intending to overtake another shall in compliance with Rule 9(e) (i) indicate her intention by the following signals on her whistle :

– two prolonged blasts followed by one short blast to mean ‘I intend to overtake you on your starboard side’;

– two prolonged blasts followed by two short blasts to mean ‘I intend to overtake you on your port side’;

(ii) the vessel about to be overtaken when acting in accordance with Rule 9(e)(i) shall indicate her agreement by the following signal on her whistle:

– one prolonged, one short, one prolonged and one short blast, in that order.

(d) When vessels in sight of one another are approaching each other and from any cause either vessel fails to understand the intentions or actions of the other, or is in

doubt whether sufficient action is being taken by the other to avoid collision, the vessel in doubt shall immediately indicate such doubt by giving at least five short and rapid blasts on the whistle. Such signal may be supplemented by a light signal of at least five short and rapid flashes.

(e) A vessel nearing a bend or an area of a channel or fairway where other vessels may be obscured by an intervening obstruction shall sound one prolonged blastThe term 'prolonged blast' means a blast of from four to six seconds's duration.Â . Such signal shall be answered with a prolonged blast by any approaching vessel that may be within hearing around the bend or behind the intervening obstruction.

(f) If whistles are fitted on a vessel at a distance apart of more than 100 metres, one whistle only shall be used for giving manoeuvring and warning signals.

Equipment for Sound Signals is based on the length of your boat as follows.

Boats less than 39.4 feet in length - must carry an efficient sound producing device. In general, this may be a bell, whistle, or air horn. Though guns--even pots and pans--can make a suitable sound signal useful in getting attention in an emergency, you should always carry the appropriate equipment.
Boats at least 39.4 feet to less than 65.6 feet in length - Must carry a whistle and a bell. The whistle must be audible for 1/2 nautical mile. The mouth of the bell must be at least 7.87 inches in diameter.

Sound signals are to be used only when vessels are in sight of each other and are meeting or crossing at a distance within half a mile of each other. These signals must never be used in fog or other conditions of reduced visibility, where the vessels are not visible to each other by eye. Only the fog signals listed under the Inland Rules, Rule 35 may be sounded at such time.

Sound signals are called "blasts". There are two different blasts used for warning and steering signals.

Short Blast - Lasts about one second.
Prolonged Blast - Lasts from four to six seconds.

Maneuvering Signals

There are different blasts combinations for various movements on the water that may use both short and prolonged blasts. When power-driven vessels are in sight of one another and meeting or crossing at a distance within half a mile of each other, each vessel underway, when maneuvering as authorized or required by the Inland rules must use the following sound signals.

One Short Blast - This means "I intend to leave you on MY port side". When you pass near another boat, you will manuever by leaving them on your left side as you pass. If you are behind another boat, going the same direction and about to overtake it, one short blast means: "I intend to pass you on YOUR starboard side, MY port side".
One Prolonged Blast - This means you are leaving a dock or departing your slip. It signals to others a change in status and that you are getting underway. A prolonged blast is also sounded when a vessel is approaching a bend in a river where vessels coming from another direction cannot be seen. It is sometimes referred to as the “blind bend signal".
Two Short Blasts - This means "I intend to leave you on MY starboard side". When you pass near another boat, you will manuever by leaving them on your right side as you pass. If you are behind another boat, going the same direction and about to overtake it, two short blasts means: "I intend to pass you on YOUR port side, MY starboard side."
Three Short Blasts - This means you are operating in astern propulsion, for example backing away from a dock
One Prolonged Blast + Three Short Blasts – This is technically two different signals in succession. One prolonged blast indicates you are getting under way, and three short blasts indicate you are backing up. This is what is sounded when you are departing a dock in reverse.
Five Short Blasts - This is the DANGER signal. Remember, that when you approach another vessel and hear either one or two short blasts, and you both understand their signal and can safely let them do it, then you are required to respond with the same signal in response. However, if you don't understand their intentions, or feel that their proposed maneuver is dangerous to either vessel, then you are required to sound the DANGER signal.

Note: Inland Rules regarding sound signals are occasionally different from International Rules. Inland Rules signal intended action and International Rules signal what you are actually doing. The following information reflects Inland Rules. If you travel overseas, you must learn the International Rules.

Proper Sound Signals

When you meet an oncoming vessel, and wish to pass port to port, you are required to sound one short blast with your horn. If the other boat is in agreement, they should respond with a similar blast.

If you approach another vessel head on, and wish to pass it on its starboard side, you are required to sound two short blasts with your horn. If the other vessel is in agreement, they should sound the same signal in response.

When you are planning on passing another vessel from behind, there are several things you must do. Any vessel that is overtaking another must keep out of the way of the vessel being overtaken. This means that you can't expect them to move, slow down, or change their course. If you plan on passing them on THEIR starboard side, you must sound one short blast. If they understand your signal and agree, they will sound one short blast in response. The vessel being overtaken has a responsibility to maintain course and speed in order to minimize the potential for collision.

When you are planning on passing another vessel from behind, there are several things you must do. Any vessel that is overtaking another must keep out of the way of the vessel being overtaken. This means that you can't expect them to move, slow down, or change their course. If you plan on passing them on THEIR PORT side, you must sound two short blasts. If they understand your signal and agree, they will sound two short blasts in response. The vessel being overtaken has a responsibility to maintain course and speed in order to minimize the potential for collision.

Note: These are not the only rules concerning sound signals in restricted visibility; there are additional rules concerning sound signals that may be found in the Rules of the Road or in Chapman's Piloting.