The explosive O’Mahony struck 15 minutes from the end when he raced onto a probing kick from midfielder Jim O’Donoghue before punching the decisive goal past advancing goalkeeper Ken O’Halloran.
Up to then very little separated the sides, but, spurred by O’Mahony’s all-important goal, St Finbarr’s finished on a high note.
The Barr’s got off to a great start against the wind with points from their left-wing pairing of Paul Murphy and Greg Leahy in the opening three minutes, and it took Bishopstown a long time to find their feet.
After their very hesitant start, Bishopstown, with two pointed frees from centre-forward Jack Ferriter, came back to level in the 23rd minute. But St Finbarr’s, who lost three players through injury in the first-half (Roy Leahy, Paul Murphy and Rory McCarthy) were not going to be outdone and left corner-forward Greg Leahy impressed with his point scoring.
Bishopstown struck their best patch just before the break. Midfielder Robert Honohan levelled the game for the second time in the 27th minute and then John L. O’Sullivan and Denis Crowley edged their side into a 0-7 to 0-5 interval lead.
Within seconds of the restart Barr’s cut the deficit to the minimum with a smart point from centre-forward Adi Callinan and the scene was set for a battle royal.
Both sets of midfielders had their moments of glory but Ronan Curran was most influential when the Blues struck for victory in the closing quarter. Bishopstown held a one point advantage when O’Mahony pounced in the 45th minute and although Bishopstown battled bravely, Barr’s put the game beyond their reach with three late points from O’Mahony, substitute Colin O’Sullivan and Adi Callinan.
: St. Finbarr’s: R. O’Mahony 1-2; G. Leahy 0-3; A. Callinan 0-2; J. O’Donoghue 0-2; C. O’Sullivan 0-2; P. Murphy and R. Curran 0-1 each. Bishopstown: J. Ferriter 0-4 (0-3 from frees); J. L. O’Sullivan 0-2; D. Crowley 0-2; D. Murphy, J. O’Shea and R. Honohan 0-1 each.
: K. McTiernan; C. Lyons, M. Shields, P. O’Brien; R. McCarthy, M. Ryan, R. Dwyer; J. O’Donoghue, R. Curran; I. Keller, A. callinan, P. Murphy; R. Leahy, R. O’Mahony, G. Leahy. Substitutes. C. O’Sullivan for R. Leahy (injured); T. Olden for Murphy (injured); A. Cronin for McCarthy (injured); A. O’Shea for Keeler.
: K. O’Halloran; C. O’Malley, P. O’Callaghan, J. A. O’Sullivan; N. O’Donovan, S. Murphy, T. Hayes; R. Honohan, D. Cullinane; J. L. O’Sullivan, J. Ferriter, D. Murphy; A. Coomey, D. Crowley, J. O’Shea.
: N. Barrett (Carrigtwohill).