He doubled the advantage midway through the second spell with a timely run to the front post to meet a dipping, swinging corner that effectively sealed the result.
Wanderers captain Adam Mitchell got one back when he reacted quickest to a bouncing ball inside the six-yard box to make it 2-1, but Masaki Nomoto's stubbed free kick in the style made famous by Cristiano Ronaldo put the match away.
McNab was understandably happy to have added to more goals to his first national league effort last week.
"It took me a while to get my first goal last week, but to get two this week was great," McNab said.
"Hopefully it's not too little too late and we just have to keep going. If we keep winning we can have a respectable finish.
"It didn't matter who we were playing or where we were playing - we needed a win.
"Morale is good at training, but on the pitch things weren't coming off."
WaiBOP coach Peter Smith had challenged McNab during the week to lead the side and was chuffed the tactic had paid off.
"I laid it down to Jack earlier in the week," Smith said.
"I said this is your ground mate, your stomping ground, and you've scored a bucket load of goals this year and done exceptionally well for Tauranga City, and I asked him whether he could replicate that for us.
Smith was happy his side had kept its shape well despite some serious pressure from their young opposition.
The sides' only visit to Mount Maunganui this season drew a solid crowd.
