In the seventh inning, Yankees second-base prospect Damon Sublett singled and James McOwen (Mariners) was hit by a pitch before Posey grounded a two-out single up the middle, his fourth straight game with an RBI. Alonso followed with a run-scoring single and crossed the plate on a double by Giants farmhand Roger Kieschnick.
Posey extended his hitting streak in Hawaii to nine games and is batting an even .500 with six multi-hit efforts in 10 games.
Alonso (Reds) also doubled in the first and singled in the sixth and Sublett hit a two-run homer in the fifth for the BeachBoys (13-11), who completed a three-game sweep of the Sharks (13-11).
Yankees prospect Andrew Brackman (3-3) allowed two runs -- one earned -- on four hits while striking out seven and walking one over six innings. The former first-round pick has 27 strikeouts in 25 2/3 innings in Hawaii. Dodgers prospect Jordan Pratt struck out five in two hitless innings, and David Pfeiffer tossed a scoreless ninth for his second save.
Mets farmhand Roy Merritt (1-2) gave up two runs on one hit while recording one out for the loss. Honolulu starter Satoshi Nagai fanned 11 while allowing two runs on seven hits in six innings, lowering his ERA to 1.80. The Japanese right-hander leads the league with 35 strikeouts over 30 innings.
Dominic Brown (Phillies) had two hits and Greg Veloz (Mets) doubled and scored for the Sharks (13-11), who dropped their sixth straight.
Steve Conley is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.