There are two layers here. First is that the US Coast Guard finally got around to writing a laboratory - testable - definition for its old "Visible X miles" ambiguous and untestable brightness rule
. You can't apply that new test, unfortunately, because you don't have the equipment/laboratory. The second is that they then certified various nav lights, with their bulbs, such that if you use a different bulb your light is not certified and you incur some sort of liability.
It's easy to find LED bulbs for older fixures that vastly out perform the certified bulbs as measured by direct observation (yours). Using them could increase your safety
while also increasing your liability. Personally, I think the lighting
required on a ship/boat is pathetic when put against the multitude of shore lights in most congested harbor areas. You can easily lose a boat that is bearing down on you, or run up on an anchored boat.
That's a head
scratcher. My answer is to go with certified bulbs, but increase the other lighting
of the boat, in our case by using LED rope
light to outline part of the boat, the wheelhouse and boatdeck in our case, so that other skippers have some way of perceiving the size and the orientation of our boat whenever we are near. Our other approach has been to turn on the spreader lights when in low visibility crowded spaces.
As a further complication, the USCG has been on a tear of late against boaters who use additional lights in ways that obscure their nav lights, particularly colored LEDS near the red and green. We keep ours white/yellowish and away from the nav lights.