I've owned the '91 for a while now, and while messing around with it a couple of days ago, I found that the driving lights have a hi/lo beam wired into them. Kinda cool. I'd really never taken the time to find out what the unlabled switches actually do as two of them are disconnected at the switch .. but the top 3-position switch controls the driving lights. The other two, I suspect, control the trailer lighting as it's wired for both 4way and 5way plugs on the transom.... I haven't checked the bulbs out... they look like a standard aftermarket chrome rectangle driving/fog light... and I wonder if it's just the bulb??