EAST HAMPTON, N.Y. -- Proponents of ethanol see it as a fuel additive that can relieve the nation's energy woes. Pleasure boaters like Walter Kaprielian say they need it like a hole in the hull. Mr. Kaprielian's 1969 boat was made in Miami by Bertram Yacht, whose sturdy older vessels have a devoted following. But the 20-footer, a beamy craft with a small cabin, has had all sorts of things go wrong with it since marinas here began selling nothing but ethanol-blended gasoline two years ago. The boat has spent the summer sitting in a repair yard while its owner...