If old outboards get your motor running, there's no better source for information or better reading than The Old Outboard Book, 3rd Edition, by Peter Hunn ($22; International Marine, 800/262-4729).
A diehard Evinrude or Johnson buff? You'll need a copy of Evinrude-Johnson and the Legend of OMC. Got a thing for Mercurys? Then it's Iron Fist: The Lives of Carl Kiekhaefer. Both by Jeffrey Rodengen ($40 each; Write Stuff, 800/900-2665).
Information about outboard power during its early years was largely compiled with the help of the Antique Outboard Motor Club Inc. (www.aomci.org). Parts books and other sources were used for the 1970s and onward. A special thanks to Peter Hunn for confirming the results.