This was a big win for the Ollie Horgan side against a never-say-die Cabinteely side.
Harps led 3-0 after less than half-an-hour but the league newcomers kept battling.
Kevin McHugh fired Harps ahead after just nine minutes from the penalty spot, after Michael Funston was taken down in the box.
On 22 minutes McHugh made it 2-0 and then just before the half hour mark Nathan Boyle scored the third.
Cabinteely pulled one back on 52 minutes through Karl Byrne.
Conor Foley got a second goal for Cabinteely on 90 minutes but it was too little, too late.