Marte also homered in the eighth and Gaby Sanchez capped the scoring with a ninth-inning solo shot for the streaking Pirates, who remained one game behind National League Central-leading St. Louis with the victory.
Jeff Locke (7-1) extended his unbeaten streak to 15 consecutive starts, limiting the Mariners to two runs on four hits over seven innings. He walked two and struck out four.
Seattle's Joe Saunders (5-8) was roughed up for six runs on six hits over just 1 2/3 innings.
Justin Smoak clouted a two-run homer and Kyle Seager added a bases-empty blast for the Mariners.