With an estimated 4,000,000 outboard motors now in use in the U.S. and an expected sale of another half-million before the end of the year, the fast-growing sport of stock outboard racing looks forward to an even bigger boom in the future. A fortnight ago the American Power Boat Association ran off its national stock championships at De Pere, Wis. and drew 16,000 spectators to make it the biggest and best ever held. After three days of thrills, spills and chills, eight new champions were named in the different runabout and hydroplane classes. First boat across the line was not always the winner as disqualifications for jumping the gun or hitting a buoy were numerous. In the first race, 13 out of 16 starting boats were disqualified.