HOUSTON -- Felix Hernandez continued his recent string of strong outings with another dominant performance against the Houston Astros Sunday.
Hernandez threw six shutout innings, scattering four hits and striking out seven to lead the Seattle Mariners to a 12-5 win, their straight.
Nick Franklin had two hits, including a grand slam, while Dustin Ackley tied a season high with three hits for the Mariners, who swept their second straight series for the first time since sweeping the Minnesota Twins and Cleveland Indians August 17-22, 2012.
Hernandez (11-4) has not allowed a run in his last two starts, spanning 14 innings and has won sixth straight. He has not allowed a run in two starts against the Astros this season, giving up just nine hits and striking out 16 over 12 innings.
Houston lost its fifth in a row and eighth in the last nine games to fall to a major-league-worst 33-64. Jose Altuve and Jake Elmore each had two hits for the Astros.
Franklin capped off a seven-run second inning with his first career grand slam to give the Mariners (46-52) a 7-0 lead.
Kendry Morales started the inning with a single before Kyle Seager reached on an error by Elmore. After Jordan Lyles struck out Justin Smoak, Michael Saunders walked to load the bases.
Ackley scored on a single, and Henry Blanco plated one more after getting hit by the first pitch he saw. Brad Miller singled to left to up the lead to 3-0 before Franklin's grand slam.
Seattle tacked on three more in the fifth as Raul Ibanez led off the inning with a double and scored on a Morales single. After Lyles hit Seager, Smoak singled to chase the right-hander with the bases loaded.
Lucas Harrell induced Saunders to ground into a fielder's choice, plating Morales to extend the lead to 9-0 before Ackley's sacrifice fly extended Seattle's advantage to 10-0.
Miller upped the lead to 11-0 with a run-scoring single in the seventh before Houston got on the board with an RBI single by Altuve in the bottom half of the inning off Hector Noesi.
Saunders made it 12-1 with a run-scoring double in the eighth.
The Astros scored four in the ninth as Brandon Barnes had an RBI-single and Justin Maxwell scored on a Matt Dominguez sacrifice fly. Barnes and Elmore came around to score on a wild pitch and an errant throw to first by Blanco after Jason Castro struck out.
Lyles (4-4) gave up a career-high 10 runs -- nine earned -- on eight hits with two walks and three strikeouts in four-plus innings. His previous career high for runs allowed was nine against Milwaukee on August 1, 2012.
NOTES: Even though the Mariners saw their franchise-record 23-game home run streak snapped Saturday night, Seattle entered the game still third in the majors with 119 homers this season. ... A day after Astros LHP Erik Bedard took himself out of a no-hit bid after 6 1/3 innings, Houston manager Bo Porter said he was not going to let Bedard, who was at 109 pitches, go past 120 pitches. ... OF Michael Saunders extended his hitting streak to 10 games with a double in the eighth.