Outside of Harry Sekhon (43) and Ashton Pattenden (41), who put on an important 57-run stand, no one stood out with the bat as City were bowled out for 153.
They almost pulled off a top defence as Tim King's offspin proved tough to get away, giving him a return of 3 for 34, but Maungakaramea held firm with important digs from Raman Sharma (40), Manvee Singh (21) and Manjot Singh (18) helping them get home.
Meanwhile Kamo High grabbed a convincing seven-wicket victory over Whangarei Boys' High School.
Cale Pooley's 56 was the backbone of WBHS' innings of 131 as the bowling of Connor Bolton (3 for 22) and Max Turner (2 for 25) kept them well contained.
Kamo High made fairly light work of the chase, getting to the total with just three wickets down.
Brett Weber scored 35, while Nathan Parkes' unbeaten 48 continued a top season for the youngster and put his side in a good position to make the final.
Onerahi picked up their third straight win after a tough start to the competition, this time grabbing a 58-run result over Kerikeri.
Batting first, Onerahi scored 207 for seven with a flamboyant unbeaten 67 from Ryan Woodman leading the way.
Woodman showed a brutal edge with four sixes during in his innings, while Pieter Lambrechts added a run-a-ball 38.
Jasmeet Singh (2 for 19) and Campbell Shepherd (2 for 21) kept Onerahi under control, while spinner Max Hart bowled well without reward.
In reply, Kerikeri fell short as a middle-order collapse either side of the drinks break made the going tough.
Luke Halligan scored a composed 41, while No 9 Shine Fulton added some late fireworks in his 39. Adam Sylva was the best of the Onerahi attack with 3 for 24.
The final round will be played this Sunday.
