The victory propelled Waikiki (14-11) into sole possession of first place in Hawaii Winter Baseball's Eastern Division.
Posey has been a key contributor during the winning streak, going 15-for-27 with 12 RBIs and 11 runs scored. Overall, the No. 5 pick in the June First-Year Player Draft has hit safely in 10 consecutive games to get his average up to .512.
In this one, the 21-year-old catcher/designated hitter reached on an infield single in the fourth inning and led off the sixth with another base hit. Fellow first-rounder Yonder Alonso (Reds) followed with a single and Posey came all the way around to score on an error by center fielder Gregory Burns (Marlins).
Roger Kieschnick (Giants) lifted a sacrifice fly to give the BeachBoys a 2-0 lead and Yuji Onizaki of Japan's Tokyo Yakult Swallows added an RBI single.
The lead was enough for Yuhei Takai (2-1), who struck out five over five scoreless innings. The 23-year-old left-hander from the Swallows walked three and struck out five.
Cubs Minor Leaguer Blake Parker served up a two-run homer to Marlins catching prospect Chris Hatcher in the bottom of the seventh, but Jeremy Papelbon (Cubs) recorded the final out for his league-leading fourth save.
The game was halted after seven innings by mutual agreement.
Pirates farmhand Kyle Bloom pitched five shutout innings for the CaneFires (12-13), but Cliff Flagello (Orioles) gave up three runs on four hits over the final two frames.
The loss was West Oahu's third straight.
Daren Smith is an editor for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.