McEwan (31), the regular Otago No 1 during the past decade, shot scores of 71, 66, 66 and 72 for a four-round total of 13-under par 275 and the Russell Hayward Memorial Trophy.
With four holes to play, he threatened the lowest four-round total of 273 since the inception of the SBS-sponsored event in 1977.
An innovation of cash prizes to help offset the vast expenses our young golfers face results in McEwan being $1500 richer as the top individual.
With 71 and 66 he held the lead at the halfway stage by a single shot from Manawatu-Wanganui No 4 Lachie McDonald, but his 6-under 66 on Sunday morning gave him a six-shot lead over Auckland No 1 Sam An.
McDonald received $500 for his Saturday morning 65, the lowest score during the weekend.
McEwan was 1-over-par after five holes on Sunday morning but made seven birdies in the last 12 holes, including birdieing the final three holes for his 66.
In the final round he was 2-under with four holes to play and needed one further birdie to beat the tournament record of 273 set by Australian Rohan Blizard in 2007.
His best chance was on his second-last hole, the par-5 Long Tom, but he drove out of bounds and finished with a disastrous double-bogey 7. His impressive sub-par golf gave him the win by three shots from An.
Otago had started Sunday in seventh place in the team event but McEwan's captain's knock lifted his team into a tie for third with Wellington - one shot behind defending champion Manawatu-Wanganui, in second.
The team tournament looked like being a repeat of last year when Auckland and Manawatu-Wanganui were tied on 282 after the first round.
But the strong Auckland quintet opened up an 11-shot lead after the second round.
A lack of form by Manawatu No 1 Joshua Munn was the difference between the teams on Saturday as the highly rated player posted two non-counting scores.
From that point on, Auckland was always in the driving seat, leading by eight going into the final round and eventually winning by eight shots over Manawatu-Wanganui.
Otago was tied for third with Southland which made up nine shots in the final round to share the $1000 third-place team prize.
The Otago quintet of McEwan, Kayne Wardell, Samson Kim, Mitch Bosley and Michael Smith gave Otago its best placing in the strokeplay event for many years.
Otago's good performance on Sunday also gave the team the Founders trophy, which the province last won in 2004.
