SEATTLE -- Starling Marte got the Pirates started with a triple -- and it only got better after that.
Marte opened the game with a triple and hit solo shots in the second and eighth for the first multihomer game of his career.
"We had some power jump out there tonight," Pittsburgh manager Clint Hurdle said.
Locke (7-1) limited Seattle to two runs and four hits, leaving him tied for second in the National League with a 2.06 ERA. He struck out four and walked two.
"Probably had the lightest stuff he's had all season. But at the end of the day, looking at his numbers, he still found a way to keep the game in check," Hurdle said.
Brandon Inge hit a three-run shot in the second inning, his first home run since last August. Russell Martin and Gaby Sanchez also went deep for the Pirates in their first five-homer game since July 22, 2009, against Milwaukee.
It was the second time this season the Mariners have allowed five long balls. Houston connected five times on April 9.
"They always say that hitting is contagious. It's true, when one guys goes, another one goes," Inge said. "It's something we just rolled with."
Kyle Seager hit his 10th home run in the sixth for the Mariners. It was the sixth that Locke has allowed this season, first by a left-handed hitter.
Marte rattled his first-inning triple into the right-field corner and scored on Jordy Mercer's groundout.
That was as much damage as Mariners lefty Joe Saunders (5-8) allowed in his previous start Wednesday at the Los Angeles Angels, when he gave up his only run on a wild pitch in a complete-game, 1-0 loss.
Saunders couldn't complete two innings this time as the Pirates chased him with five runs in the second.
"It was just a bad night for him," Mariners manager Eric Wedge said. "They came in swinging the bats. He just made some mistakes and some of those don't come back."
Martin opened the inning with his home run to center, his eighth. With one out, Tony Sanchez singled and Neil Walker walked. Inge, with two hits in his previous 32 at-bats, connected for a three-run shot to left on a 2-2 pitch for his first homer since Aug. 1 with Oakland against Tampa Bay.
"I don't like zeros in that stat," Inge said. "Just get that one out of the way. Now I can relax and do my normal swing. A lot of times when you're trying to hit home runs, especially me, it doesn't work."
One pitch later, Marte homered to right-center.
"Bad start, bad start. All nine hitters, the ball was up in the zone and down the middle of the plate," Saunders said. "I could go on and on. Just a bad one."
"I think it was a lack of execution, and he'll be the first to tell you," Hurdle said. "We saw his 1-0 complete game. We've seen him effective many times. Making the pitch he needed to or wanted wasn't really there. It happens up here."
The Mariners scored a run in the second on Carlos Triunfel's two-out single to center. Seager opened the sixth with his home run to right on a 2-1 pitch from Locke.
Marte hit his eighth homer with two outs in the eighth on the first pitch from Carter Capps. Sanchez hit his seventh in the ninth off Capps.
- The last time Saunders worked just 1 2-3 innings was Aug. 7, 2009, with the Angels against the Rangers. His career low is two-thirds of an inning on Sept. 30, 2006, with the Angels against the A's.
- The Pirates have had eight scheduled days off this season, including one Monday. They are 8-0 in the first game after an off day.
- Before the game, the Mariners placed CF Franklin Gutierrez on the 15-day disabled list (strained right hamstring) and recalled OF-2B Dustin Ackley from Triple-A Tacoma.