Tim Wakefield (9-3) allowed two runs in six innings to improve to 6-0 at Fenway Park this season.
Chris Volstad (4-7) allowed nine hits and a career-high eight runs before he was chased in the fourth, when the Red Sox sent 11 batters to the plate. It was his fourth consecutive loss.
Ortiz, who did not homer in the first six weeks of the season, now has five for the year
-- four of them in the last nine games. His batting average is back up to .210
-- still 73 points below his career average, but at least not below the Mendoza line, .200, where he stayed for most of the last month.
Ortiz homered into the Marlins bullpen to lead off the fourth, then came up again with the bases loaded and two outs and singled up to make it 8-1.
Nick Green had two hits and two RBIs for Boston, and Jacoby Ellsbury had two hits, two stolen bases and scored twice, including a dash from second on an infield single in the second.
Chris Coghlan, who was 7 for 14 over weekend, went 2 for 4 and drove in both runs for Florida, which swept Toronto over the weekend but failed to reach .500 for the first time since May 13.
Notes: Wakefield made his 380th career start for Boston, two behind Roger Clemens for the most in Red Sox history. He has 90 wins at Fenway, five behind Clemens. ... It was Boston's 499th straight sellout at Fenway Park.