John Bayne, the manager of the Serviceman electrical and heating firm, won the race by an hour from Brent Harris (Auckland) in a time of 7hr 24min 10sec.
He was defending the title he won last year, and his time was 4min 48sec faster.
But it was even tougher this year as the runners had to contend with temperatures in the mid 30s (degC). A blustery headwind also sapped competitors' energy, and nearly 300 people did not finish the race.
"It was a lot hotter and the blustery wind blew dust around off the gravel road," Bayne told the Otago Daily Times yesterday.
"It was a real battle out there."
Organisers said conditions were the second-worst they had seen since the event started 15 years ago.
Only nine of the 17 solo runners completed the race.
Bayne was hoping to break 7hr for the race.
Former Otago runner John Thirkettle holds the record of 6hr 36min.
Bayne was on target when he passed halfway in 3hr 16 min but the headwinds took their toll later in the race.
"I was on target at 60km but then the wheels fell off," Bayne said.
"The last quarter of the race was hard when when the heat and the wind combined to slow me down. I got cramps and exhaustion."
Bayne was the third runner home over all, and only two of the 55 four-man teams that finished beat him.
Harris, the second-placed solo runner, required medical attention at the finish.
Bayne was talked into running the Molesworth ultra-marathon in 2006 by his Dunedin running mate Jamie Sinclair, who finished sixth on Saturday in 9hr 30min 01sec.
Bayne was one of Fred Strachan's star pupils at the North End Rowing Club in the 1980s and represented New Zealand in the lightweight eight at the world championships in Milan in 1988.
The crew finished fifth.
"Running is harder than rowing," Bayne said.
"You have got to be careful because it is easier to get injured. "In rowing, you can throw your body about because it is a low-impact sport. The races are shorter and you recover faster."
Glen Ferguson (Leith) broke a lap record with his time of 1hr 20min 08sec when he spearheaded the winning team, which also included former Dunedin school teacher Ian Thomas from Blenheim, who was timed at 1hr 24min 34sec.
Two other Blenheim runners were in the team, which finished in a combined time of 5hr 28min 02sec.
Billy Hebbard ran 1hr 22min 49sec and John Kennedy 1hr 23min 31sec.
