The masthead light should be visible in a 225 degree arc centered on dead ahead.
Straight ahead and starboard
A powerboat less than 39.4 feet long is anchored at night white light must be visible from all directions.
If you are operating a powerboat at night your green side light must be visible to boats approaching over an arc of the horizon 112.5 degrees and so fixed as to show the the light from right ahead to 22.5 degrees abaft of the beam on its respective side.
Rule 21 of the Navigational Rules of the Road. (a) "Masthead light" Means a white light placed over the fore and aft center-line of the vessel showing an unbroken light over an arc of the horizon of 225 degrees and so fixed to show the light from right ahead to 22.5 degrees abaft of the beam on either side of the vessel, except that on a vessel of less than 12 meters (39'4") in length the masthead light shall be placed as nearly as practical to the fore and aft center-line of the vessel.
Rule 21 It must show an unbroken light over an arc of the horizon of 225 degrees and so fixed as to show the light from right ahead to 22.5 degrees abaft of the beam.
A white light on a powerboat (that obviously doesn't have a mast) must be displayed so as to be visible from 360 degrees.
You are approaching a powerboat head-on
You are approaching a powerboat head-on
You are approaching a powerboat head-on
Bubbles visible in the glass with the system operating.Bubbles visible in the glass with the system operating.
Registration number
Registration number
There have been a number of questions about boating lights here recently, so I'm assuming this is another.The answer to this one is complicated, and depends on:1. If the boat is a sailboat or a powerboat (sailboats which also have motors are considered powerboats if the motor is in use).2. If the boat is in motion or at anchor.3. The size of the boat.You should really be a lot more specific with the question if you want a definitive answer; specifically you should say whether it's a sailboat or a powerboat, if it's under sail/power or at anchor, and how long the keel is.