The defending champions have dropped out of the playoffs.
Harbour turned a 17-10 deficit into a 23-17 win in brutal conditions at Kettle Park No 2 to oust the Grizzlies.
The win saw the Hawks improve from fifth to fourth and they will play University at University Oval in the first round of the playoffs on Saturday.
University were the big movers in the final series of round-robin games.
They trailed Kaikorai 13-9 at halftime. But they made good use of the crosswind at Hancock Park to storm to a 36-13 victory.
They rocketed up the standings from seventh to third, while Kaikorai slipped from third to sixth.
Taieri held on to beat Southern 24-14 at Kettle Park No 1.
The win means they qualified in the top spot and will host Kaikorai at Peter Johnstone Park.
The loss saw Southern drop down a spot to fifth and they will play Dunedin at Kettle Park.
In the other game, Alhambra-Union beat Zingari-Richmond 27-15 to record their first win this season.
Both sides were not in playoff contention. But it is a morale-boosting win for Alhambra-Union who avoided a winless season.
They still finished in last place, however.
