Southwick finished with 209 passing yards on 17-of-29 efficiency, while Aaron Burks hauled down five passes for 107 yards and a touchdown as Boise State (8-2, 6-1 MWC) bounced back after a loss to San Diego State last week.
Jay Ajayi paced the Broncos' ground game with 54 yards and a touchdown.
Hawaii (1-8, 0-6), meanwhile, remained winless in conference play as starting quarterback Sean Schroeder was held to 10-of-19 passing for 100 yards and an interception.
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