Mamabolo set the pace at the 50km Old Mutual Om Die Dam marathon in warm Hartbeespoort conditions on Saturday, only to be beaten by fellow Nedbank runner Colin Parura. The Zimbabwean claimed gold by crossing first in 2:53:54.
It was the second time in succession that Mamabolo came second at this event, but he believes his time (2:56:51) was a great improvement from last year and should get him ready for the Comrades Marathon in June.
Incidentally, he also finished second there last year, although he did win it in 2012.
"I'm not too disappointed to finish second. Hopefully victory will come soon," said Mamabolo afterwards, adding his rivals profited from copying his strategy throughout the race.
"When I increased the pace, they did the same. When I slowed down, they also slowed down. But overall it was a great race. I have a knee injury but I was still able to pull through.
"I should compete at Comrades."
In the women category, Caroline Wöstmann defended her title by winning in 3:29:47, followed by Charné Bosman (3:34:42).
Obed Kopong (1:10:50) clinched the men's half marathon, while Andronica Mokgotla (1:26:40) triumphed in the women's section.