The Yankees opened a 10-game western road trip by winning their fourth in a row.
Phil Hughes (3-4) went seven innings to get the victory, blanking the Mariners on three hits with seven strikeouts.
He received all the support he needed when New York brought 11 men to the plate in the third inning.
Seattle's only run came off reliever Boone Logan on a double by Kyle Seager in the eighth.
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