Mamobolo, who finished second in 2010, took the lead after four hours of running to secure victory on Sunday.
Lebohang Monyele took the early lead in the 87th edition of the race, but was caught by fellow novice Gert Thys shortly before the halfway mark.
Thys, the SA record holder in the standard marathon, had said before the race he was confident of setting a new course record.
He blew up spectacularly, however, after going through the halfway stage at Drummond with a lead of more than seven minutes over the other real contenders.
Mamabolo took the lead after four hours of running and tore clear to bag the first local victory in the race since Sipho Ngomane won in 2003. – Sapa