In their next match against Bethlehem College, Boys' High batted first on the second day and totalled 218 for nine wickets in their 50 overs.
Opener Chamodh Peiris led the way with 47 but there were handy contributions too from his opening partner, Crawford, and also Lobb, Coutts, Mitchell and Caleb Boswell-Smith.
Bethlehem College never threatened the total as they were bowled out for 108, with the medium-pacers, Boswell-Smith, Lobb and Matt Kingi claiming eight wickets among them.
On day three, Boys' High squared off against the other unbeaten team in their pool, St Paul's Collegiate of Hamilton.
The home team struggled to score in the face of tight bowling and committed fielding from the Whangarei side and had reached just 94 runs by the time of the second drinks break at 34 overs.
However, with wickets in hand, they hit out well to reach a total of 215 for eight wickets in their 50 overs.
Losing their first wicket to a run out, Whangarei were soon three down for 31. A good partnership then developed between Coutts and Lobb before another run-out derailed the innings.
Max Trimble hit out boldly to keep hopes alive until he was caught on the boundary, at which point the chase was virtually over. St Paul's won by 58 runs.
On the last day, St Paul's comfortably beat Hamilton Boys' High in the final, while Whangarei played St Peter's School, Cambridge for third place.
Whangarei's total of 203 for six wickets was based on two good partnerships, 91 between Peiris and Lobb, and then 76 between Peiris and Tim Osbaldiston. Both Peiris, 82, and Osbaldiston, 58 not out, posted their first half-centuries for the team.
St Peter's appeared to be struggling in reply at 161 for seven wickets but a combination of tired bowling, untidy fielding and reckless but ultimately successful running by the batsmen saw them through to a win with two overs to spare.
Scores
WBHS 144 (Fletcher Coutts 61, Dante Mitchell 26) beat Gisborne BHS 108 (Josh Crawford 4/26, Matt Lobb 2/12, Fletcher Coutts 2/21).
WBHS 218/9 (Chamodh Peiris 47, Caleb Boswell-Smith 35, Fletcher Coutts 27, Dante Mitchell 26, Josh Crawford 25, Matt Lobb 23) beat Bethlehem College 109 (Caleb Boswell-Smith 3/15, Matt Kingi 3/18, Matt Lobb 2/17).
St. Paul's Collegiate 215/8 (Matt Lobb 2/36, Fletcher Coutts 2/46) beat WBHS 157 (Matt Lobb 31, Fletcher Coutts 30, Max Trimble 20).
WBHS 203/6 (Chamodh Peiris 82, Tim Osbaldiston 58 n.o., Matt Lobb 25) lost to St Peter's School, Cambridge 204/7 (Caleb Boswell-Smith 2/33).