Coetzee was at 12 under on the Els Club course at Copperleaf Golf Estate.
Mark Tullo of Chile shot a 66, while Dawie Van Der Walt of South Africa was also at 11 under after 14 holes in the co-sanctioned European and Sunshine Tour event.
Fifty-four of 156 players were unable to complete their round. Among them was two-time Masters champion Jose Maria Olazabal of Spain, who needs to birdie one of his closing two holes to make the cut.
Former U.S. amateur champion Peter Uihlein birdied three of his closing four holes for a 66