Ortiz led the offensive charge that led to a miserable night for Harang, who barely made it through five innings. After Seattle held a 5-1 lead after two innings in Tuesday's game, the Red Sox have outscored the Mariners 21-7 in the following 16 innings.
"It wasn't a very good ballgame at all," Seattle manager Eric Wedge said. "We didn't play very well at all."
Coming off a strong start against Cincinnati, Harang was roughed up by the Red Sox bats. He gave up eight hits and seven runs, and was pitching from behind most of the night.
He also allowed Ortiz's record-setting double leading off the second inning that gave the Boston slugger 1,689 career hits as a DH, passing Harold Baines for the most all-time. An inning later, Ortiz hit his 19th homer of the season, a two-run shot that gave Boston a 4-0 lead.
Ortiz was acknowledged by a standing ovation from the mix of Red Sox and Mariners fans and appeared touched by the response, tipping his helmet twice toward the standing fans and patting his chest as the milestone was shown on the video board. Ortiz already held the marks for the most runs scored, doubles, home runs, extra-base hits and RBIs by a designated hitter.
"I've seen too much of him over the years," Wedge said. "He is about as professional a hitter as you can be. Still has the bat speed, still has the power, commands the strike zone as good as anybody in the game."
It was the third time this season Harang (4-8) has been knocked around for at least seven earned runs. He failed to strike out a batter for the first time all season and his three walks allowed were a season high.
"They made me work. I was falling behind in the county early on and you can't do that with a lineup like that. You have to try and get ahead early and I wasn't doing that," Harang said. "You start throwing more strikes over the plate and a veteran lineup like that, they're going to take advantage of that and make you work."
Boston broke the game open in the sixth and knocked out Harang after singles by Jose Iglesias and Brock Holt to open the inning. Jacoby Ellsbury and Shane Victorino both had RBI singles in the four-run inning that was helped along by a throwing error from Seattle shortstop Brad Miller.
Ellsbury extended his hitting streak to 18 games, the longest current streak in baseball.
Ortiz's milestone night overshadowed one of the best starts this season by Boston's Felix Doubront. With its bullpen taxed in the opening two games of the series, Doubront (6-3) provided the outing Boston needed to give its relievers a rest.
Doubront took a shutout into the seventh and silenced a Seattle offense that scored 19 runs against Boston pitching in the first two games of the series. He allowed only a pair of early singles, and a double to Michael Saunders the first Seattle batter to reach second base in the fifth.
Seattle finally got to Doubront in the seventh when Jason Bay led off with a double and scored on Henry Blanco's two-out single. But that was the extent of Seattle's offense against the lefty.
"We'll take a strong outing off a starting pitcher every night that we walk in here," Boston manager John Farrell said. "I think the biggest thing is he continued to put up zeroes after we scored runs and that kept the momentum on our side."
Seattle shortstop Brendan Ryan led off the eighth with a solo homer off Boston's Brandon Workman, making his major league debut. Seattle scored three times in the inning.
Notes: Ellsbury returned after missing the first two games of the series with a sore wrist. ... Seattle RHP Stephen Pryor (60-day DL, lat muscle), threw a 25-pitch simulated game on Wednesday and will do the same on Saturday. Wedge said OFs Michael Morse (quad) and Franklin Gutierrez (hamstring) are not yet ready to go out on rehab assignments. ... Farrell said RHP Alex Wilson, placed on the 15-day DL Tuesday, has joint inflammation in his thumb, but the injury is not as serious as first believed.