(a) Motorboats subject to the provisions of this chapter shall be divided into four classes as follows:—

Class A. Less than sixteen feet in length.

Class 1. Sixteen feet or over and less than twenty-six feet in length.

Class 2. Twenty-six feet or over and less than forty feet in length.

Class 3. Forty feet or over.

(b) Every motorboat in all weathers from sunset to sunrise shall carry and exhibit the following lights when underway, and during such time no other lights which may be mistaken for those prescribed shall be exhibited.

1. (1) Every motorboat of classes A and 1 shall carry the following lights:—

   First. A bright white light aft to show all around the horizon.

   Second. A combined lantern in the fore part of the vessel and lower than the white light aft, showing green to starboard and red to port, so fixed as to throw the light from right ahead to two points abaft the beam on their respective sides.

2. (2) Every motorboat of classes 2 and 3 shall carry the following lights:—

   First. A bright white light in the fore part of the vessel as near the stem as practicable, so constructed as to show an unbroken light over an arc of the horizon of twenty points of the compass, so fixed as to throw the light ten points on each side of the vessel, namely, from right ahead to two points abaft the beam on each side.

   Second. A bright white light aft to show all around the horizon and higher than the white light forward.

   Third. On the starboard side a green light so constructed as to show an unbroken light over an arc of the horizon of ten points of the compass, so fixed as to throw the light from right ahead to two points abaft the beam on the starboard side. On the port side a red light so constructed as to show an unbroken light over an arc of the horizon of ten points of the compass, so fixed as to throw light from right ahead to two points abaft the beam on the port side. The said lights shall be fitted with inboard screens so set as to prevent these lights from being seen across the bow.

3. (3) Motorboats of classes A and 1 when propelled by sail alone shall carry the combined lantern, but not the white light aft, prescribed by subsection (b)(1) of this section. Motorboats of classes 2 and 3, when so propelled, shall carry the colored lights, suitably screened, but not the white lights prescribed by subsection (b)(2) of this section. A motorboat of classes A, 1, 2 or 3 of subsection (a) of this section when propelled by sail alone if not otherwise required or authorized by this section to carry one or more lights visible from aft, shall carry at her stern a white light, so constructed that it shall show an unbroken light over an arc of the horizon of twelve points of the compass, so fixed as to show the light six points, from right aft on each side of the vessel. Such light shall be carried as nearly as practicable on the same level as the side lights. In a small motorboat propelled by sail alone, if it is not possible on account of bad weather or other sufficient cause for this light to be fixed, an electric torch or lighted lantern shall be kept at hand ready for use, and shall, on the approach of an overtaking vessel, be shown in sufficient time to prevent collision.
4. (4) Every white light prescribed by this section shall be of such character as to be visible at a distance of at least two miles. Every colored light prescribed by this section shall be of such character as to be visible at a distance of at least one mile. The word ''visible'' in this subsection, when applied to lights, shall mean visible on a dark night with clear atmosphere.
5. (5) When propelled by sail and machinery every motorboat shall carry the lights required by this section for a motorboat propelled by machinery alone.