A much stronger finish by Maynooth Post Primary in extra-time sent them through to the next round of the Leinster championship yesterday.
They outscored their opponents by four points to one in the crucial second period of extra-time for an emphatic win.
A goal by Darrenn Dempsey for Portmarnock had forced the fixture into extra-time.
MAYNOOTH PP: D Conway; D O'Neill, A Sweeney, C Cushin; C O'Neill (0-1), G McMahon, F Molloy; M Creevy, K Carr (1-1); B Downey (0-1), D Comerford (0-1), P O'Rourke (0- 2); A Ferris, A Dalton (0-4, all frees), A Baxter (1-1). Subs: S Kane for Ferris, R Moore for Cushin and D Carty (0-1) for Creevy.
PORTMARNOCK CS: M Doyle; P Norton, N Whelan, R Lenihan; S O'Carroll, B McDonagh, C Rickard; S Walsh, F McGowan; A Breen (0-5, all frees), D Walsh, N Minihan; D Dempsey (2- 1), S Price (0-2, frees), I Forde. Subs: N Monk for Forde, R Colreavy for Norton, I Forde for Monk.
Referee: D Hendrick (Dublin).