Boone hit a three-run triple and Sexson, playing while he appeals a two-game suspension, had a two-run homer as the Mariners embarrassed the slumping Padres 14-5 on Friday night.
The Mariners hit three triples in a five-run fifth -- the first time in franchise history -- and had a season-high nine extra-base hits at spacious Petco Park. The Mariners hit three triples in a game for the first time since May 13, 1987, at Boston.
Seattle tied season highs in runs and hits (17), and the 14 runs were the most allowed by the Padres at Petco Park, which opened last year. Every Mariners regular, plus starter Gil Meche, had at least one hit. Meche also had his first career RBI.
Boone had three hits, three RBI and scored three runs in his third game since returning from a four-game benching to work with hitting coach Don Baylor. In his previous two games, he was just 1-for-7.
"It's good to see a smile on his face for a change," manager Mike Hargrove said.
"I'm not going to get ahead of myself," said Boone, who raised his average to .233. "It was a good night. But before I get excited, I'm going to have to string it together for a couple of weeks. But it was a good beginning.
"And it was a great win for us," Boone said. "We haven't had too many laughers, where we can kind of relax. It seems like every game comes down to the wire. It's nice to be able to relax a little bit and have a game like that."
Sexson was suspended and fined an undisclosed amount by Major League Baseball earlier Friday for throwing a bucket of baseballs on the field in front of Seattle's dugout after he was ejected for arguing a called third strike last Saturday against the New York Mets.
The right-hander hit his 17th homer, a 404-foot shot in the fourth to right-center, the part of Petco Park that Padres sluggers have had the most trouble reaching. The deepest part of the park is the right-center gap at 411 feet.
With the game tied at 4, the Mariners opened the fifth with consecutive triples by Ichiro Suzuki and Randy Winn to chase starter Darrell May. Tim Redding came on and walked Adrian Beltre and hit Sexson in the side with a pitch to load the bases. With one out, Boone tripled into the gap in right-center, then scored on Mike Morse's sacrifice fly to make it 9-5.
"Right-center, at 411, that is huge," Boone said. "But other than that, I play at Safeco. You're used to that. But I didn't hit any balls tonight that normally would be home runs. I expect them to be doubles."
The NL West-leading Padres continued their June swoon, losing their third straight and for the 15th time in 22 games this month. They also fell to 5-11 in interleague play.
San Diego's Dave Roberts homered leading off the fifth, then left the game with a strained patella tendon in his left knee.
May (1-2) wasn't anywhere near as sharp as he was on Sunday, when he beat Johan Santana and the Minnesota Twins 5-1. He allowed six runs and six hits in four innings.
"We were off tonight," manager Bruce Bochy said. "May didn't have his sharp command, then we let the game get out of control from the fifth inning on. We did swing the bats better. Unfortunately, our pitching was not there tonight."
Meche (8-4) struck out a season-high seven in five innings. He allowed five runs -- four earned -- and seven hits.
The Padres blew a 3-0 lead for the second straight game. They also did it in losing to the Los Angeles Dodgers on Thursday, 4-3 in 10 innings.
San Diego went up 3-0 in the second on four hits, a walk and an error.
Meche had his first career RBI when he singled in the third to score Morse. Sexson tied it with his homer in the fourth, then Morse hit an RBI double for a 4-3 lead.
The Padres tied it at 4 on Xavier Nady's homer in the fourth, his sixth.
Seattle added four runs in the eighth and one in the ninth.