 Shares of Generac Holdings Inc. GNRC, 2.63 sank 10.7 toward a more than two-year low in premarket trading Wednesday, after the maker of home and industrial power systems reported third-quarter profit and sales that fell well below expectations and cut its full-year outlook, citing disappointing residential sales. Net income fell to 58 million, or 83 cents a share, from 132 million, or 1.93 a share, in the year-ago period. 