The Expedient Africa team rider finally secured victory in his home race on Saturday after fighting off the challenges of Andrew Hill and Tyronne White in tight a 42km battle.
In the women's race, Pietermaritzburg's Christie Hearder (Team Absolute Motion) was able to secure a race-winning gap over Bell Equipment's Hayley Smith on the first major climb of the race and then hold off the challenge of her South Coast rival for the rest of the event.
At the finish line Hearder had held her lead of just over a minute, despite spending much of the race looking over her shoulder and battling to keep Smith at bay.
Marais was ecstatic to have finally emerged with a win in his sixth attempt to claim the Mandela Day MTB Dash. The Howick resident has had six near misses that included numerous podium finishes but never a spot on the top step, until Saturday.
"I am so stoked to have won this at last," said the fulltime professional rider. "It is about time. I have been trying since this race started and I have had thirds and seconds numerous times.
"It went pretty well today but it was never easy. I came and rode a new section of the course on Monday and after seeing that I started the race with a bit of a plan that I would attack early and try and get away on the first climb.
"I tried that, and then when I got to the finish I was asking myself: 'Why did I go so hard at the start?'
"On the first climb I pushed hard and Andrew (Hill), Tyronne (White) and myself got away and then it was just a matter of consolidation and trying to play tactics to get a winning advantage. On the final major climb of the day, at St Ives with about eight kays to go, Andrew and I were able to drop Tyronne.
"It was quite a technical climb and Tyronne, being third in the line must have been struggling with all the roots and stuff. When you are third you cannot really see them so it is harder and we managed to get a gap.
"And then on the next piece of single-track I was able to get a bit of a gap on Andrew and from there it was just a case of trying to hold on to the finish.
Marais crossed the line in 1:38:12 with Hill, who a week ago finished on the podium of a marathon event in Germany, finished just 19 seconds behind with White just over a minute further back.
"I am mostly happy with the results," said Hill after the finish. "I flew back on an international flight from Germany on Wednesday so I was not expecting fireworks from my legs, but part of them seemed to arrive at the start.
"Stu has home-ground advantage, so he has got that knowledge and he is a very good, strong cross country rider. He has the legs for the short, kicker climbs out there today. If it had been longer I may have been able to challenge him, but this is his type of riding and he is riding extremely well at the moment."
In the women's race Smith made sure Hearder had to work hard for her victory.
"This race is always hard," said Hearder soon after crossing the line. "I did not do it last year so I found it tougher than I expected â€¦ and I always find 40km races so hard. In a 60km race you can pace yourself, but 40, yoh, it is always hard.
"I had Hayley Smith chasing me all the way. I got away in the beginning on the first long climb. In the single-track Hayley caught me a bit because she is faster than me in technical riding and then on the climbs I had to work hard to build a gap because I know her strength in the singlet-rack."
Despite working hard for her win, Hearder found the race particularly rewarding for more than just the victory and the R10 000 cheque.
"For us we are just racing, but Nelson Mandela built a whole legacy and so to race in his honour at this event is awesome.
"I also love this event just to see the development guys and to see how they have developed over time. I saw some of the young guys out on course today and it was incredible to see how well they are riding â€¦ they are flying and it is because of events like this."
1 Stuart Marais 1:38:12
2 Andrew Hill 1:38:31
3 Tyronne White 1:39:48
4 Dean Van Dyk 1:48:18
5 Sithembiso Masango 1:48:24
6 Ethan Jackson 1:48:26
7 Mitchel Potgieter 1:48:37
8 Kusaselihle Ngidi 1:48:54
9 Hendrik Bester 1:49:18
10 Nhlanhla Mhlanga 1:51:58
1 Christie Hearder 2:02:58
2 Hayley Smith 2:04:21
3 Claudia Slattery 2:13:58
4 Shelley Higgo 2:14:00
5 Nadine Nunes 2:18:01
6 Chloe Bateson 2:22:50
1 Nicholas Burczak 51:00
2 Sipho Kupiso 52:04
3 Nkululeko Pewa 53:28
4 Chad Stevenson 53:53
5 Thuia Ngidi 54:52
1 Riley Smith 1:07:20
2 Jodi Mackinnon 1:08:26
3 Amy Salvesen 1:14:58
4 Madison Bateson 1:18:59
5 Lara Bateson 1:19:52