Very useful diagram Inertia, explains what you mentioned earlier very clearly! So even if I were to run 6v through a 3v there arent going to be any negative effects?
Cheers, Tex
Running a 3 volt lamp off 6 volts will be bright, but short lived, unless there is something in the circuit to limit the current - as Dave shows in his diagram, another identical 3 volt lamp.
Whether using incandescent or LED, the usual problem for nav lights is that they are too bright. The cure for incandescents is to run with a bit less voltage (say, 4.8 instead of 6), for LEDs, a higher value ballast resistor does the job. I've watched ships at sea at night, because nav lights "only" fulfill a legal need, they tend to be the last thing you see if deck lights are on. Deck lights are much brighter because the crew need them to see to do work, and that is a cost with a return.