David, I recall my switches were getting hot, too. The voltage drop was so bad that my instruments would reset themselves, depending on how many lights were on.
If your boat is anything like mine, I don't think breaking the lights into three zones will fix all the problems. In my case, this was related to the panel design as it aged. I recall one positive wire from the battery, which is connected to one fuse via a crimped on terminal connection, which is connected to the next fuse via a short jumper with crimped terminal connections, which is connected to the next the same way, etc. The result: current to some fuses has to go through, say, 20 jumper wires and 40 terminal connections first! This works fine when the boat is new from the factory, but after 25 years, the terminals corrode and more resistance develops. So the panel itself becomes a big resistive heating element. ;-)
My $0.02: Invest in a good, accurate voltmeter. (I've got a very nice Fluke meter that I love.) Turn on all the lights. Measure the voltage difference between + and - at the battery. Then work outwards, looking for voltage drops. You should be able to isolate how much of this is due to the wire run between the battery and the panel, internal resistance within the panel, and resistance along each circuit branch to the light.
In my case, I needed a new positive and negative wire to the panel, and a better distribution scheme at the panel. The positive from the battery fed a bus, which has one positive wire leaving it per circuit and going to each panel fuse.
Good luck!
Ryan
Tesara, #337
