Mervue cruised to a 3-0 lead at half time, Pat Hoban putting them in front with a 19th-minute penalty before tapping home from close range six minutes later.
Etanda Nkololo added another four minutes from the break, but Longford hit back after 54 minutes when William McDonagh scored on his debut.
Alan Murphy put the ball in his own net to make it 3-2 after 57 minutes, before goalscorer Hoban was sent off. Sub Tom King found the net for Mervue eight minutes later before he was red-carded for dissent after 74 minutes. By then Longford had reduced the margin to a goal when Alan Kirby scored from close range after a pass from Gary Shaw.
The pair reversed roles for the equaliser in the final minute when Shaw headed home Kirby’s free-kick.
In the third minute of injury-time Mark Salmon kept his nerve to slot home a winning penalty at the end of a dramatic encounter.
MERVUE UNITED: O’Malley; Keogh (Walsh 76), Elwood, Conneely, Casserly; Varley, Nkololo, Murphy (Kelly 58), Ludden; Molloy (King 61), Hoban.
LONGFORD TOWN: Hyland; Lee, Hope (McDonagh 22), Haverty (Griffiths 83), Deans; Salmon, James, Gillepsie (Kirby 46), Crawley; Bermingham, Shaw.
Referee: P Caschera.
Limerick FC 3 Finn Harps 0
By Bernard O’Neill
High flying Limerick FC struck in either half to record their second win of the season over Finn Harps at Jackman Park last night.
Limerick broke the deadlock just before the half hour when James McGrath’s shot from a Gary Sheehan cross was deflected into his own net by Sean McGowan.
The insurance goal finally came in the 75th minute after Shane Tracey slotted home from the spot after Derek O’Brien was fouled.
Rory Gaffney completed the scoring in the 90th minute.
LIMERICK FC: Ryan, Kelly, Purcell, Tracy, Treacy, O’Leary, Bradley, Sheehan (O’Brien 72), McGrath, Behan (McGann 77) Brosnan (Gaffney 52).
FINN HARPS: Gallagher, Bonner, Coll, O’Hagan, Cowan, McMonagle (Doherty 60) McGowan, McBride, McHugh (Clarke 67) McVeigh, Merritt (McGinty 79).
Referee: S Grant (Wexford).
Athlone Town 2 SD Galway 0
By Kevin Egan
First-half goals from Jason Hughes and Tommy Barrett secured all three points for Athlone Town in this First Division tie, but SD Galway will feel disappointed they didn’t at least reduce the deficit during a second-half in which they enjoyed plenty of possession.
Hughes opened the scoring in the 22nd minute with an excellent strike from 20 yards and Barrett followed up with a close range header six minutes later.
ATHLONE TOWN: P Jennings; J Woods, B McCarthy, T Barrett, N Scullion; D Rushe; K Williamson, V Feeney, B Gill, J Hughes; M Sherlock.
Subs:. L Sung for Barrett, N McGee for Feeney, I Sweeney for Scullion
SD GALWAY: L Grant; N Curran, P Quinlan, C Fadden, E Greaney; G Dolan, W Enubele, L McConnell, T Bradshaw; M Tierney; E Curran.
Subs:. C Burke for E Curran, M Harty for McConnell, T Molloy for Bradshaw.
Referee: Conor Fitzgerald.
Wexford Youths 1 Waterford Utd 2
Classy Sean Maguire scored one and created the second as he inspired Waterford Utd to all three points over a disappointing Wexford Youths in this Division 1 game at Ferrycarrig Park last night.
In the first-half both sides struggled to make an impact. The game was scrappy and tight so it was no surprise when the opening goal came from a mistake.
Peter White drove in a shot from the right that was spilled by keeper Graham Doyle, leaving Sean Maguire to tuck a low shot into the net. Waterford looked the more likely to take control but against the run of play the home side forced an equaliser. Keeper Packie Holden had a rash challenge on Aidan Keenan just inside the area with referee Kevin O’Regan immediately pointing to the spot. Danny Furlong saw his penalty spilled by Holden but the inrushing Dean Broaders found the net which left it 1-1 at the interval.
The second-half produced some scrappy football before Waterford regained the lead in the 79th minute. Sean Maguire cut in from the right but keeper Graham Doyle only pushed his shot back into the pat of Peter Keegan who had the simple task of tapping the ball into an empty net.
WEXFORD YOUTHS: Doyle, B Nolan, S Corcoran, Carr, Browne, Dempsey (Croke 86)), Broaders, Malone (Molloy 86), Keenan (Elmes 62), Furlong, Wall.
WATERFORD UTD: Holden, Carey, Mernagh, Dempsey (Coad 75), Long, Burns, Ryan (McGrath 8), White, Keegan (Keane 82), Maguire, Phelan.
Referee: Kevin O’Regan (Kerry).