Here (attached) is the lower unit of my 1971 Evinrude Twin Ski 40 that I bought this summer. I recognize the vent plug for the lower unit oil, near the top of the picture. (I think I can just make out the words, "OIL VENT" by it.) As for the fill-plug, I see a smaller screw head that takes a phillips screwdriver at the top of the rudder; but that doesn't look like what I expect a lower unit drain plug to look like. However, I don't see anything else! Is that it, or am I missing something? Thnx...