Rule 23 — Power-driven vessels underway

(a) A power-driven vessel underway shall exhibit:

(i) a masthead light forward;

(ii) a second masthead light abaft of and higher than the forward one; except that a vessel of less than 50 metres in length shall not be obliged to exhibit such light but may do so;

(iii) sidelights;

(iv) a sternlight.

(b) An air-cushion vessel when operating in the non-displacement mode shall, in addition to the lights prescribed in paragraph (a) of this Rule, exhibit an all-round flashing yellow light.

(c) A WIG craft only when taking off, landing and in flight near the surface shall, in addition to the lights prescribed in paragraph (a) of this Rule, exhibit a high intensity all-round flashing red light.

(d) (i) A power-driven vessel of less than 12 metres in length may in lieu of the lights prescribed in paragraph (a) of this Rule exhibit an all-round white light and sidelights;

(ii) a power-driven vessel of less than 7 metres in length whose maximum speed does not exceed 7 knots may in lieu of the lights prescribed in paragraph (a) of this Rule exhibit an all-round white light and shall, if practicable, also exhibit sidelights;

(iii) the masthead light or all-round white light on a power-driven vessel of less than 12 metres in length may be displaced from the fore and aft centre line of the vessel if centreline fitting is not practicable, provided that the sidelights are combined in one lantern which shall be carried on the fore and aft centre line of the vessel or located as nearly as practicable in the same fore and aft line as the masthead light or the all-round white light.

MSN 1781 (M+F): Rules text stated on the document as amended through IMO Res A.910(22); read with MSN 1781 (M+F) Amendment 3 (21 Nov 2023, current — replaces Amendment 2; scope-only change for the Merchant Shipping (Watercraft) Order 2023). Per Amendment 2 Appendix 2, the only later wording changes are Annex IV (A.1004(25)) and new Part F Rules 39-41 (A.1085(28)).

Contains public sector information reproduced under the Open Government Licence v3.0. Source: MSN 1781.

Independent preparatory study aligned to the MCA OOW (Yachts <3000 GT) oral examination syllabus. Not an MCA-approved course and confers no credit toward a Certificate of Competency.