Not so fast Benny! There are three wires!
There are two bulbs at the top of the mast on a H23.5, and three wires in the cable that goes up there. I think the three-position switch on the electrical panel is labelled "Anchor" and "Steaming" (left and right), with OFF being in the middle position. "Anchor" turns on both lights for all-around lighting; "Steaming" just the forward one.At least, that's how my H23.5 is set up. The link below shows the Perko masthead light on my boat.BTW, my masthead lights didn't work when I bought my boat, a 1995 that was 7 years old. After replacing the bulbs and a lot of testing, it turn out the problem was just corrosion on the connector at the mast base. I cleaned up the prongs and the sockets with a "Starbrite Corrosion Buster Pen":http://www.starbrite.com/sproductdetail.cfm?ID=1502There may be better ways. Careful with the pen; it sheds fiberglassy bits that you don't want stuck in your skin or eyes....RickM...