The win was deserved, but the margin flattered Dunedin when it beat Harbour at Watson Park.
Dunedin led 8-0 at the break after winger Joe Bradley scored late in the first spell after flanker Jon Crossan had come in as the extra man.
When lock Michael Gurran scored early in the second spell the margin was stretched to 15-3 and Harbour was forced to take risks and play catch-up rugby.
The light drizzle made the ball slippery and the Harbour backs made mistakes as they tried to break the disciplined Dunedin defence.
The midfield tackling of Michael Walding and Simon Davey did not give the Harbour backline any leeway.
The last two Dunedin tries by fullback Josh Hamilton and substitute loose forward Andrew Mackintosh stretched the winning margin to 26 points.
Dunedin dominated in the forwards with its strong front row.
Prop Will Henry had a good game, while hooker Adam Duhig took two tightheads.
Gurran was dominant in the line-out, and loose forwards Crossan, Tim Fraser and Scott McKee made life difficult for the Harbour backs and won the battle at the breakdown.
First five-eighth Shaan Davis had his kicking boots on and landed four goals from his six attempts to score nine points.
Players to impress for Harbour were flanker Jason Kelly and midfield backs Doug Edwards and Cory Kara.
Dunedin 29 (Josh Hamilton, Joe Bradley, Michael Gurran, Andrew Mackintosh tries; Shaan Davis 3 conversions, penalty goal), Harbour 3 (Jonnie Hughes penalty goal).
Half-time: 8-0.
Referee: Tim Baker.
