Baltimore, MD (SportsNetwork.com) - Steve Pearce hit his first career grand slam and the Baltimore Orioles topped the Seattle Mariners 5-4 in the rainy rubber match of a three-game series at Camden Yards on Thursday.

Tommy Hunter (2-1) earned the win after escaping a bases-loaded jam during the eighth prior to J.J. Hardy's go-ahead RBI single in the home half.

"Huge win for the club," said Pearce. "We won the series and now we get to bring that momentum on the road."

Rickie Weeks supplied a pinch-hit, two-run single and Welington Castillo and Logan Morrison brought in a run apiece for the Mariners, who were coming off a 4-2 win on Wednesday.

Neither starter factored into the decision due to a two-hour, 17-minute rain delay. Baltimore's Chris Tillman surrendered one run on one hit and three walks over three innings, while Seattle's J.A. Happ gave up four runs on four hits over two frames.

Chris Davis led off the home eighth with a single off Danny Farquhar (0-3), moved up to second on Pearce's groundout and hustled home on Hardy's grounder up the middle for a 5-4 lead.

"I thought our bullpen did a great job, we just gave up that run at the wrong time," said Farquhar.

Zach Britton struck out two in a flawless final frame for his ninth save of the season.

The Orioles wasted no time getting on the board. Jimmy Paredes reached on a fielder's choice with one out. Two batters later, Delmon Young singled and Davis walked to load the bases. Pearce gave Baltimore a 4-0 lead with one swing of the bat as he crushed a first-pitch changeup just over the wall in left.

Castillo got a run back for the Mariners in the second with a sacrifice fly to right to score Nelson Cruz, who worked a leadoff walk.

After play resumed following the lengthy rain delay, the Mariners loaded the bases with two outs off Brian Matusz in the fourth. Weeks came on to pinch hit and stroked a grounder up the middle for a two-run single, making it a 4-3 game.

Seattle loaded the bases with three straight singles to start the seventh. Morrison's two-out walk off Darren O'Day ushered in a run to tie the game. O'Day limited the damage by striking out Justin Ruggiano for the third out.

Each team wasted opportunities with runners in scoring position. Young grounded out with men on the corners to end the seventh for Baltimore, and Willie Bloomquist followed suit in the eighth with the bases loaded.

Game Notes

The Orioles' last grand slam was hit by Jonathan Schoop against Toronto on April 11 ... Mariners third baseman Kyle Seager extended his hitting streak to seven games with two hits, but was ejected after striking out to end the fifth ... Paredes extended his on-base streak to 22 games ... The Mariners went 3- for-15 with RISP and left 13 on base.