A Boston-area amateur golfer was convicted on Tuesday of engaging in insider trading by tipping off friends about the business activities of American Superconductor Corp. Eric McPhail, 41, was found guilty by a federal jury in Boston on conspiracy and securities fraud charges following a seven-day jury trial, prosecutors said. The case proceeded to trial after a federal judge refused to dismiss the charges in light of a recent appellate ruling that narrowed the reach of insider trading laws.