Navigation lights are required on all boats underway or at anchor at night, from sunset to sunrise. Different types of boats will use specific combinations of nav lights in order to facilitate identification by other watercraft at night. Lighting requirements for pleasure craft varies by boat type and size. Generally speaking, marine navigation lights can be broken down into the following:
Sidelights: Red for the port side, and green for the starboard side. Sidelights must shine 22.5° abaft the beam and are always lit at night. Side lights may be combined into one housing as a bicolor light.
Tricolor Lights: Tricolor lights combine red and green sidelights and add a white stern light. They may be lit at night only when the boat is under sail. Tricolor lights are legal only on boats under 66 feet in length.
Sternlights: A white light mounted as close to the stern of the vessel as possible, the sternlight must shine through an arc of 135° and is always lit at night.
Masthead Lights: Also known as a Steaming Light or Bow Light, the Masthead light is white and only lit at night when the boat is under power. On sailboats, the masthead light is mounted approximately one third of the way down on the mast. On powerboats, the masthead light is sometimes mounted on a short spar or staff. The masthead light must be mounted above the sidelights. The masthead light must shine 22.5° abaft the beam on both sides so that it is visible to oncoming and overtaking vessels.
All-Round Lights: All-round lights shine through 360°. A White all-round light is is lit at night when the boat is at anchor.
Visibility range requirements (in nautical miles) vary by light type and boat size:
For Boats less than 39.4 ft. (12 meters) in length:
Boats less than 65.6 ft. (20 meters) in length:
Boats less than 164 Ft. (50 meters) in length:
LED vs Conventional Lighting
LED Navigation lighting is increasingly popular. LEDs consume less power and have longer services lives. Although service rating varies by manufacturer, a typical service life of 50,000 to 100,000 hours is touted by most. Longer life means fewer bulb replacements. LEDs can run on 12 and 24 volt systems without modification, run cooler, are highly shock and vibration resistan, and exceeds USCG requirements and ABCY A-16 certification. Standard incandescent navigation lights remain a popular and viable option for many boaters. Less expensive than LED lighting, there is a wider variety of models and styles available with standard bulbs.
Portable Navigation Lights are designed for boats under 23 feet in length and for boats without electrical systems. These portable light systems are typically powered by D-Cell or AA batteries. Portable lights resemble flashlights in appearance. and are available with LED or Krypton bulbs. Configurations include suction cup mounts, C-clamp mounts or glue-on mounts for inflatable boats.
Remote Control Searchlights are installed on larger craft can serve as a nighttime piloting aid and as an emergency signal when needed. Some models can be directed by a wireless remote control. A hand held searchlight on smaller craft may also serve the same functions. These lights typically feature high power halogen bulbs that provide candlepower ratings from 100,000 cp to 3,000,000 cp.
Deck Floodlights add a large margin of safety when crew members are working on deck at night. Available with sealed beam bulbs, halogen bulbs and low power LED bulb construction.
Spreader Lights are similar in size and function to deck floodlights but are optimized for use on sailboats. Deck illumination is an important safety concern for nighttime sailing. Available with sealed beam bulbs, halogen bulbs and low power LED bulb construction.
Underwater lights are designed to be submerged and illuminate the waters below the hull. Popular for night time fishing expeditions due to their fish attraction qualities, underwater lighting systems are suitable for offshore use, night diving, or as colorful accent lighting at the dock. Mounting requires either a 2" diameter hole in the hull (thru hull style) or surface mounting with a smaller hole for wiring and screws.
Underwater lights are offered in thru-hull styles (requiring a 2" diameter hole in the hull), and surface mount configurations (requires a smaller hole for wiring and mounting screws).
The Chapman Book of Piloting and Seamanship is the essential guide for power and sail boaters. It contains an extensive chapter on navigation lights, rules, regulations and how to interpret running lights.
Understanding the Rules of the Road by Paul Boissier, offers a dynamic approach to collision avoidance, as well as explaining standard lights, shape and sound signals vessels use to communicate with each other.