The Bay of Island pack was responsible for the side taking a comfortable 24-8 lead into halftime but, spurred on by a slick backline, Whangarei came back in the second half.
"You have to give Whangarei their due - they threw everything at us and we were forced to make tackle after tackle for almost the entire final 20 minutes," Hewitt said.
He praised his players' attitude particularly when under the pump in the second spell.
"You could tell what it meant to them to win after the whistle - and that's why this competition is important, it's a chance to discover representative players on our own doorstep by giving club players something higher to play for," he said.
BOI try scorers were Quinn Butler, Ram, Matere Tauroro, Steve Watene and Morris Cooper.
Earlier, the Northern Wairoa-Rodney selection beat Mangonui 41-7 for third place in the competition.
The games were followed by a presentation, function and a hangi.