Bill Mueller had three hits and two RBI, and David Ortiz went 2-for-2 and drove in two runs for the Red Sox, who are assured of being alone in first place at the All-Star break for the first time since 1995. The Red Sox lead the New York Yankees by 3½ games and Baltimore by four.
"We just need to win tomorrow," Boston manager Terry Francona said. "That stuff takes care of itself."
Baltimore's Rafael Palmeiro got two hits to get within five of 3,000, and his eighth-inning home run was his 564th, moving him past Reggie Jackson into sole possession of ninth place on the career list.
But the Orioles dropped below second place for the first time since April 9, so Palmeiro wasn't in the mood to speak about his quest to become the fourth player in major league history to have 3,000 hits and 500 home runs.
"I just want to get it over with so we can stop talking about it," he said. "We lose a game and we're talking about this. It's just not right, in my mind."
The Orioles have gone 3-12 since June 21, when they held a two-game lead over Boston.
"We just need to play better," said Jay Gibbons, who went 0-for-4. "If we keep playing like this, it will get out of hand quickly."
Boston's Bronson Arroyo (7-5) gave up two runs and six hits in 7 2/3 innings, striking out three and walking two. He had lost his previous two starts and was 0-2 with a 7.64 ERA in seven lifetime appearances against Baltimore.
"He pounded the strike zone. He was efficient," Francona said. "It looked to me he got stronger right until the very end."
Francona pulled Arroyo after Palmeiro's solo shot in the eighth. The right-hander retired 10 straight before the homer.
"I felt like I was getting a little tired, but I still had a good heater," Arroyo said.
Damon had two doubles, two singles and a walk in extending his career-best hitting streak to 23 games, the longest run in the majors this season.
"Johnny has been phenomenal," teammate Jason Varitek said. "He hits balls hard, he hits balls soft. He's a tremendous athlete that does some tremendous things."
Boston used a two-run sixth inning to chase Sidney Ponson (7-7) and take a 5-1 lead. After a single and two walks loaded the bases, rookie Chris Ray replaced Ponson and gave up a two-run single to Ramirez, who upped his major-league leading RBI total to 80.
"Once it was 5-1, it kind of broke their spirit a little bit and allowed me to pitch a bit easier," Arroyo said.
Ponson allowed five runs, nine hits and five walks in 5 1/3 innings. The right-hander is 0-3 in his last four starts.
Mueller hit a two-run single off Tim Byrdak in the eighth to make it 7-1.
Boston will close the first half with two more games in Baltimore. Regardless of the outcome, the defending World Series champions will hit the break atop the division.
"We're just trying to keep going," Damon said. "Hopefully we can get the next two games."
A two-out RBI single by Ramirez put Boston up 1-0 in the first inning, and the Red Sox added a run in the second when Ortiz got an infield hit with the bases loaded and two outs. Ramirez, seeking his 21st career grand slam, followed with a popup.
Boston made it 3-1 in the fourth. Mark Bellhorn drew a one-out walk, took third on a double by Damon and scored on a sacrifice fly by Ortiz.
- Palmeiro's first hit was a broken-bat grounder to left that foiled Boston's infield shift and ended a 1-for-18 skid.
- The Red Sox stranded 15 runners.
- Baltimore's Sammy Sosa went 1-for-3, giving him hits in three straight games for the first time since June 13-15.
- Boston has won 13 of 18.