Overnight leader Graeme McDowell (70) and former British Open champion Justin Leonard (67) were among a group of four players three strokes off the lead.
Fathauer, trying to become the sixth consecutive first-time winner on the PGA Tour, birdied the third, fifth, seventh and ninth holes to reach the turn with a two-stroke lead.
He then reached five-under for the day after a birdie at the par-five 13th.
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McDowell, fresh off an eight-under 63 in the second round, made a poor start as he followed a double-bogey at the opening hole with a bogey at the second.
But the Northern Irishman recovered nicely with four birdies over a seven-hole stretch before bogeying the par-five 13th.
The 2010 U.S. Open champion then birdied his penultimate hole to put himself in contention for his first PGA Tour win since 2013.
Bohn was cruising along with four birdies on his front nine and then followed a birdie at the 12th with an eagle at the par-five 13th before a lightning delay halted play for about 90 minutes.
He would have had a share of the lead going into the final round if not for a bogey at the 18th.
(Reporting by Frank Pingue; Editing by Tony Jimenez)
