Hi Bill,
While not a direct answer to your question, I did need to replace bulbs in my spreader lights recently. I was worried that the fixture/bulb combination would make it difficult to find replacement parts. It turned out that on my boat (no. 349) the fixture was quite serviceable and the bulb replacement was pretty easy. The bulbs were GE 4406 or 4411 "tractor" bulbs. The bulbs are rated at 35W and have screw terminal connectors on the back that accommodate a spade or fork wire terminal.
The most difficult part of the job was to figure out how to get the bulb out of the fixture. It turned out to be rather straight forward: the bulb is held in place by a big perimeter retainer spring (about 4-1/2 inches in diameter split ring) that simply settles into a recessed groove in the front (down-facing) of the lamp fixture. No need to remove the fixture from the spreader....just don't drop the big split rings when you finally get them pried loose.
I didn't really want to put in 35W bulbs, but this was the easy and low cost approach...paid about $11 each for the bulbs at an auto parts store.
