Clay Buchholz struck out 10 batters over six innings to get the win and was backed up by a Boston attack that produced seven runs during the first five frames.
Dustin Pedroia, Ortiz, Mike Carp and Jarrod Saltalamacchia each drove in a run during the first inning and the Red Sox went on to hammer Philip Hummer (0-5) for seven runs on 10 hits in 4 2/3 innings.
Ortiz hit his homer in the third, his first of the season.
Buchholz (5-0) gave up two runs on six hits in 7 2/3 innings. He has a 1.19 earned run average over 37 2/3 innings in five starts.