The masthead light is a white, forward-facing light that must be displayed by boats at night when operating under motor power. This light is often referred to as the "steaming light" (despite the fact that very few boats actually use steam power). The light must shine forward over an arc of 225 degrees. Like all navigation lights, the masthead light must be on between sunset and sunrise.
On sailboats, this masthead light is not at the top of the mast, as the name seems to imply. The light is usually placed about 2/3 of the way up the mast. The masthead light on a sailboat should not be confused with the tricolor light or the anchor light, which are both located at the top of the mast.
On vessels under 12m, the masthead light and sternlight can be combined into a single all-round white light.
|Length of vessel :||Visibility|
|over 50m (164 ft.) :||6 miles|
|20m (65.6 ft.) - 50m (164 ft.) :||5 miles|
|12m (39.4 ft.) - 50m (164 ft.) :||3 miles|
|less than 12m (39.4 ft.) :||2 miles|