Bohn, who completed a third-round 71 in the morning in the weather-plagued tournament, finished at 18-under 270. The 37-year-old Bohn also won the 2005 B.C. Open.
Overton mounted a persistent challenge, twice tying Bohn on his way to a 66.
Overton birdied the 18th, but Bohn, who made birdie putts of 5 1/2 feet on No. 15 and 22 feet on No. 16, had to only tap in on 18 for his fifth birdie of the round.
Heavy rain and lightening Friday and again Saturday morning delayed the early rounds. Bohn, who led wire-to-wire, played 24 holes Saturday and 30 Sunday.
He earned $1,152,000 after making $395,321 in his previous eight starts this year.