Olivo's two-out, two-run homer off Chen in the fourth inning gave the Mariners a 2-0 lead.
Chen hung a curveball after walking Towson University's Casper Wells with two outs, and Olivo made him pay. It's the 26th homer allowed by Chen this season.
The Mariners have been given enough chances before Olivo stepped to the plate, having stranded four runners.
The Orioles have managed only one baserunner through four innings, with Nate McLouth singling in the fourth after Ramirez retired the first nine batters.
McLouth has 11 hits in the Orioles' last eight games, and four in the last two.
Chen retired the first five batters before the Mariners loaded the bases with two outs in the second inning. Robert Andino saved two runs by backhanding Brendan Ryan's grounder toward the middle and flipping to shortstop J.J. Hardy for the force at second.
Chen threw 41 pitches in the first two innings, compared to 19 by Ramirez.
The Orioles are 34-43 when their opponent scores first.
Update: Chen failed to get through the sixth inning, leaving with one out and Justin Smoak on second base after a double.
Chen threw 103 pitches, including 12 while striking out Michael Saunders leading off the sixth. He allowed six hits, walked two, struck out two and departed with the Mariners leading, 2-0.
Chen has given up two earned runs or fewer in three of his last five starts. Manager Buck Showalter isn't pushing him much beyond 100 pitches in an attempt to keep him fresh down the stretch and perhaps in the playoffs.
McLouth has both of the Orioles' hits off Ramirez, giving him 12 hits in his last eight games. No one else with a bat bothered to show up tonight.
Update II: The Orioles finally chased Ramirez in the ninth with back-to-back singles to by pinch-hitter Ryan Flaherty and McLouth. Flaherty didn't have a hit since Aug. 25. He had batted once since that date before tonight.
McLouth now has 13 hits in his last eight games, and back-to-back three-hit nights.
Jake Arrieta has been huge out of the bullpen with 2 2/3 perfect innings.
Update III: Arrieta didn't allow a run or a hit in 3 1/3 innings. He struck out four.
Brian Matusz has stranded all 10 runners that he's inherited, including one tonight. He gave up two singles in the 10th, but Darren O'Day struck out both batters he faced to carry the game into the 11th.
Steve Tolleson, pinch-hitting for Flaherty to lead off the 11th, delivered his first hit with the Orioles since July 16. McLouth laid down a sacrifice bunt on a Charlie Furbush pitch that almost hit him in the chest. This guy can do no wrong these days.
Josh Kinney entered the game, and Hardy worked the count full before drawing a walk. Xavier Avery, who pinch-ran for Davis in the ninth, struck out in his second at-bat with the Orioles since July 8. Adam Jones was hit by a pitch for the 12th time this season, the ball drilling him in the back, but Matt Wieters struck out to end the threat.
O'Day stranded the potential winning run at second base in the bottom of the 11th by striking out Eric Thames on the 10th pitch of the at-bat, and the free baseball continues.
Johnson has allowed two earned runs in 16 1/3 relief innings.
The Orioles are playing their fifth game this season that's gone 14 innings or more, and their second that's stretched into the 17th inning. Davis isn't available to pitch in this one.
Wieters is still catching. I'll go out on a limb and predict that Taylor Teagarden is behind the plate for tonight's series finale.
Update V: The Orioles decided to score every nine innings tonight.
Mariners reliever Lucas Luetge walked McLouth to begin the 18th, Hardy singled and pinch-hitter Teagarden blooped a single down the right-field line to break the 2-2 tie. Hardy scored on Mark Reynolds' grounder.
Jim Johnson recorded his 44th save, one short of the franchise record, and the Orioles took a 4-2, 18-inning victory.
Hunter earned the win with two scoreless innings.
Teagarden has seven hits this season to go along with eight RBIs. He doesn't always get hits, but when he does, he prefers to make them game-winners.
The Mariners were 0-for-17 with runners in scoring position and left 16 runners on base. The Orioles were 2-for-14 with RISP and left 12 on base.
The game lasted 5 hours, 44 minutes. Felt like 5:43.
The longest game in Orioles history lasted 19 innings on June 4, 1967. They flirted with history at Safeco Field, but settled for pulling into a first-place tie with the Yankees in the American League East.
The Orioles are 14-2 in extra innings, with 14 straight victories. They're 20 games above .500. They improved to 4-61 when trailing after the eighth inning.
Go to bed.