Poor wording by me. You are quite right regarding incandescent lamps, I
should have noted the comment related to halogen lamps. I also think it is
the least likely cause of his problems. Regarding the halogen lamps
undervoltage will not stop them working as such but will greatly shorten
lamp life.
One thing that intrigues me however is that Harlan refers to his boat as a
J100. Now I'm not being adamant about this but I was under the impression
that J100s have only been on the market a couple of years. If thats correct
it all seems a tad strange to me. To begin with the J100 brochure says that
they come with all necessary nav lights and given the age in which we live
I'd have thought that would have meant masthead installation, yet Harlan
says he stepped on his lights and that he does not even have an allround
white steaming/anchor light, working or not. That seems strange in a boat so
young.
My boat is nearly twenty years old and is only now beginning to have these
kind of problems with nav lights. Sadly mine is definitely a masthead
installation and the problems all appear to be around 13 metres above the
deck. Bugger !!
Cheers
Andrew

"Mark" wrote in message
ups.com...

tdw wrote:
First up you should check the size of the wiring up the mast. If it is
undersized
you will have severe voltage drop problems and this will contribute to
the
lack of reliability.

Undersized wiring with its associated voltage drop just means the
lights will glow less brightly, and may not meet Coast Guard
specifications for brightness. Incandescent bulbs *like* lower voltage
and last longer. Shouldn't affect reliability. Assuming it's not also
crappy wiring with compromised insulation, or ridiculously undersized,
like 22 gauge or smaller.

Corrosion at contact points is usually the problem; check switches,
fuse carriers, connections, bulb mounts, etc.