They had a classic match as McEwan, well aware of the overall situation, used his experience down the closing stretch. "I am getting too old for this, I was shaking far too much," he joked.
"We are over the moon, it has been an awesome week and these boys just keep on fighting," said McEwan.
In the final, Waikato beat Otago 4-1 to win the title for the first time in eight years.
Unlike last year when they had just squeezed through on a halved result with Tasman, Manawatu-Wanganui were the first team to confirm a semifinal spot with the Auckland victory, with McDonald and Lock both victorious over James Eng and Johnny Tynan, McDonald continuing his unbeaten streak at No3 at that point.
"We came into the week as one of the teams to beat and this was always our goal to make the semifinals, so it's nice to get it done," said the left-hander.
"We are still unbeaten and it is nice to have that momentum. We did what we needed to do and it is nice to follow up last year after the success at North Shore.
"It gives us the confidence that we can do it. We know what to expect because we have been here before."
At that stage, the team did not seem to have any specific concern about playing Otago, even when the southerners beat perennial contenders Bay of Plenty to book the last semifinal spot, reversing a 5-0 loss to BoP in last year's semifinals.
"It doesn't really matter who we play. All of the teams are really solid and there are no easy matches," said McDonald.
"The Otago team is stacked full of good players and we know that they will be up for it."
Manawatu-Wanganui finished top of Division 1 with four victories, two draws and 22 individual game wins.
"It is just awesome. It is pretty much why most of us play golf. You get those goose bump feelings," said No1 player Josh Munn about the tournament.
"When you are under the gun and when you pull it off there is no better feeling and it is just awesome."
However, there may have been some flutters following the draw with Wellington as McDonald lost his streak to Marc Jennings and Lock was beaten by Daniel Hillier.
Then the next morning on Saturday, only Munn would pick up a win in the Otago match-up, beating Mark Brooks 4-3 as Otago ended Manawatu-Wanganui's run.
They have still been one of the strongest teams at the 15-team amateur national match-play tournament in recent seasons - coming runners-up in 2012, champions in 2013 and semifinalists this year.