Sales of water heaters and boilers in the U.S. and foreign markets increased by double digits, helping A.O. Smith Corp. to boost profits in the first quarter of 2015, the Milwaukee-based company said Friday. Net income for the quarter that ended March 31 was $58.4 million, or 65 cents per share, an 11.7 percent increase compared with $46.7 million, or 51 cents per share, in the same quarter a year ago.