When the Walkinshaw Andretti United's crew released Mostert from the pitlane after a tyre change, he drove into the path of Tickford's Thomas Randle, forcing him to hit the brakes.
A resulting five-second penalty left Mostert to try to build a lead over fellow Ford Mustang driver Waters, but a margin of just 2.58s handed Waters his first win of the season.
Waters had snatched pole position by a narrow 0.03s, but a slip at the end of the opening lap saw him run wide and Mostert was through and away to the lead he would maintain until the penalty was determined.
"It's awesome to get a few trophies this weekend and get a win in the race," said Waters. "I got my head down and closed the gap to Chazzie. It was only two or three years ago I lost a race for a five-second penalty so it was good to get one back!"
Mostert put his hand up to take the blame for a race win lost.
"That sucks. I did not expect us to be that close to somebody else," he said. "I hesitated a little bit, that was my mistake, I'll take that one.
"I didn't really race the race I wanted to race. I probably burnt the tyres a little bit trying to get [back] that penalty. He [Waters] eased into it, he drove a smart race."
Chaz Mostert, Walkinshaw Andretti United Ford Mustang GT
Photo by: Edge Photographics
Triple 8's Will Brown secured third place on the road, taking the place from Randle on lap 49 of the 55-lap race. But in doing so he helped Randle off the road and earned a five-second penalty of his own, which he overcame by just over one second to hold onto his second podium result of the weekend.
"I was working hard to get to him, I thought he moved under brakes. Unfortunate for him," he said. "For us to be third and second on a hard weekend, not too bad a weekend."
Randle dropped back to fifth place, splitting the Dick Johnson Racing Ford duo of Will Davison and Anton de Pasquale, who finished sixth.
It was a tough Sunday for Triple 8's Broc Feeney, who qualified outside the top 10 and could only make it to seventh place. WAU's Ryan Wood was eighth ahead of fellow Ford driver Matt Payne (Grove Racing) and David Reynolds (Team18 Chevrolet).
The results mean that Brown has extended his points lead over team-mate Feeney to 136 points.
The 2024 Supercars season will resume in four weeks, when the teams assemble for the fifth round of the championship at Hidden Valley, in Darwin, on 15-16 June.
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Source: Autosport