Leonys Martin, Jurickson Profar and David Murphy each knocked in two runs, while Mitch Moreland added an RBI and three runs scored for the Rangers, who avenged Friday's 3-1 loss in the series opener to extend their lead atop the AL West to 1 1/2 games over Oakland.
Texas starter Martin Perez (6-3) gave up a run in each of the first three frames, but managed to keep the Mariners off the board from there. The 22- year-old left-hander scattered eight hits over seven solid frames to earn his third straight victory.
"He's thrown some real good games for us," Rangers manager Ron Washington said of Perez. "Just let the kid continue to pitch and continue to have fun and continue to grow and just watch it and enjoy."
Kyle Seager stroked a solo homer and finished with two RBI for the Mariners, who lost for the third time in their last four games.
Felix Hernandez (12-6) was tagged for five runs on five hits and as many walks over five frames to absorb the loss.
Seager scorched an RBI single in the first and Brendan Ryan added a run- scoring base hit in the second, but the Rangers pushed five runs across in the home half to take the lead for good.
Adrian Beltre and Alex Rios led off with back-to-back singles before Moreland walked to load the bases. After Geovany Soto fanned, Profar looped a single into shallow right-center to plate Beltre and bring the Rangers within one.
Murphy followed with a line-drive double over the head of Dustin Ackley in center to put the Rangers on top before Martin laid down a suicide squeeze.
Seattle catcher Henry Blanco got to the ball quickly out in front of the plate, but Profar made a nice slide to evade the tag of the diving backstop, giving the Rangers a 4-2 lead.
With runners on the corners, Elvis Andrus scorched a single through the hole on the right side of the field to score Murphy for a 5-2 cushion.
Seattle got a run back in the third on Seager's one-out solo shot to right, but Perez held the M's to just two hits and a walk over the next four frames.
Gentry, who entered for Murphy as a pinch-hitter in the seventh, clubbed a two-out, two-run double to push the margin to 7-3 before Texas tacked on eight runs in the eighth to put the game out of reach.
Beltre stroked an RBI single before Moreland walked with the bases loaded to force in a run. After Soto fanned, Profar singled to short to score Beltre and Gentry reached on a fielder's choice that scored Rios.
Martin followed with a run-scoring base hit before pinch-hitter Adam Rosales hit a grounder to shortstop Ryan, whose toss to second was off the mark, allowing Profar and Gentry to race home for a 14-3 lead.
Ian Kinsler capped the outburst with an RBI double to left.
"Going into the seventh inning it's a two-run ball game," Seager said. "We were definitely in the game, we were battling and they were able to get some fortunate hits there in the eighth to really push it open."
Texas went 9-for-23 with runners in scoring position and left 11 men on base ... Seattle finished 2-for-7 with RISP ... Seattle reliever Oliver Perez was charged for six runs on five hits and two walks in two-thirds of an inning.
08/18 01:53:47 ET