Allan's 7:22 was the exact race time Manson recorded last year as runner-up, when he was 24 minutes off the pace when the 37-year-old Wanaka athlete led from start to finish.
Christchurch-based Manson rates Saturday's performance ahead of his first victory at Opotiki four years ago.
“I had to work bloody hard for it but it feels so good to get it right,” Manson posted after the race.
“Huge respect for all the competitors out there, but particularly Dougal, an incredible athlete whose level I have been trying to match for a long time.
“I'm not sure if I am exactly there yet — big D likely had an off-day, so I won't take it for granted and I will keep working hard so I can keep improving.
“But of course I'm super happy for having a great race.”
He gave a shout-out to the Motu Challenge organisers for a great event and thanked his mum and dad for being his support crew again.
Manson has long been tipped to win the world championship at the C2C one day, having come so close while finishing in the top 10 multiple times — third, fourth, fifth this year and agonisingly close runner-up in 2021 — along with several times leading the race through the Southern Alps.
Meanwhile, his upcoming race programme illustrates he is not confined to multisport events. He has entered New Zealand's premier cycle race, the Tour of Southland, this month and the Taupo Ironman 70.3 in December.
The Motu Challenge is arguably the North Island's premier multisport event. It is raced over a tough 172km of steep terrain, with 65km of mountainbike, 17km of bush run, 52km of road bike, 27km of kayaking and a final 11km bike/run combo to the finish line.
' Possibly the greatest of all time at this and other endurance races is Elina Ussher of Nelson. The veteran dominated the women's race yet again on Saturday.
The many-times C2C titleholder and 11-time Motu champion finished in 8:31, first open and vet woman, and 13th individual overall. She was 37 minutes ahead of Sarah Jenkins and Fiona Dowling.
In the teams division of the Challenge, the Gisborne-based #hear4U-ewe matters crew were fifth in the male four-person team division and 13th overall in 8:47.
Peter Blake, George Williams and Chris Cave managed to get Tim Taylor, the first solo kayaker to circumnavigate New Zealand, as a last-minute ring-in to paddle.
Gisborne's Andrew Reid and Andrew Barrett, training for the Coast to Coast, won the tandem division.
The Motu 160 is a punishing 160km mountainbike and road bike race from Opotiki to Opotiki through Motu, held within the Challenge. Gisborne team The Hoskins were fourth overall in 5:29:51 and finished first mixed pair in a small teams field.