McNeill shot a 3-under 69 to complete the tournament at 16-under 272 and bag the second PGA victory of his career.
Ishikawa shot 68 Sunday and finished at 14-under for the event. Boo Weekley and Henrik Stenson tied for third at 275.
Ishikawa scored five birdies on the back nine to make a run at the lead, but McNeill birdied the final three holes after playing the rest of the round at par with three birdies offsetting a trio of bogeys.
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