The Mariners moved back to within two points of the Sky Bet League Two play-off places with a convincing away victory over Gillingham.
Town dominated the first half in Kent and went in with the lead at the break after Andy Cook opened the scoring three minutes before half-time.
Gillingham equalised through Garath McCleary after a strong start to the second half but the visitors recovered to regain control of the game and Jaze Kabia capitalised on a mistake by goalkeeper Glenn Morris to restore the advantage with his 20th goal of the season.
From then on, Town did not look back and Kieran Green’s header made the points safe with 10 minutes to go, before substitute Charles Vernam added a fourth goal to wrap up a big win on the road.
Jamie Walker and Justin Amaluzor came in for Geza Turi and Darragh Burns as Grimsby head coach David Artell made two changes to the team that lost at Chesterfield in midweek.
Jackson Smith continued in goal, with Harvey Rodgers, Maldini Kacurri, Cameron McJannet and Reece Staunton forming an unchanged defence. Amaluzor, Green, Walker, Clarke Oduor and Kabia were the midfielders, as Cook again led the attack.
On the bench, there was a first appearance in a senior matchday squad for 16-year-old youth team winger Harvey Booth. Turi, Burns, Christy Pym, Tyrell Warren, Jayden Sweeney and Vernam were also named as substitutes.
Gillingham came into the game knowing they would definitely be playing League Two football again next season and with three fixtures remaining, Gareth Ainsworth’s side were looking to end this campaign strongly.
FIRST HALF
Smith gathered a low cross from the right as the home side were the first to attack, before Cook worked an opening for Kabia but he was well-blocked by defender Conor Masterson.
Gillingham keeper Morris got to a low cross from Staunton just ahead of the stretching Green as Town threatened again with a neat move from the left on eight minutes, then striker Ronan Hale was caught offside after a break by Armani Little.
A cross from Green was cleared after more good play by Cook, whose cushioned header gave the midfielder the ball in space on the right.
Morris caught a Staunton free kick from the right soon afterwards, then Hale shot wide from 25 yards after cutting in from the home left following another break by Little.
Town were controlling possession and looking dangerous in attack, with Oduor doing well to win a free kick near the left corner flag on 15 minutes. Staunton’s delivery was headed away as far as Oduor but his return ball into the box was cleared.
Walker fired over the bar from distance after winning the ball in midfield and another good challenge by the former Bradford City man brought Gillingham’s next attack to an end.
McCleary was caught offside when a Hale strike fell into his path in the six-yard box, before Green and Rodgers linked up to create an opening at the other end but when the ball was pulled back, Cook could only turn it wide of the near post under pressure.
Green was unable to divert a low ball from Oduor towards goal, then Rodgers saw a cross from the opposite, right flank blocked as Town kept searching for a breakthrough.
A strong run by Sam Gale down the home right did not get any reward as his low cross was comfortably cleared by Rodgers, before Green found Amaluzor with a good pass to the right but the winger’s low ball towards Cook was cut out by Masterson.
Cook fired at Morris after persistence from the striker took him into the box on 37 minutes, then a cross from Green was claimed by the keeper as the away side continued to dominate.
Green headed a long throw from Remeao Hutton away but when the ball was played back into the box, Rodgers had to turn it behind for a corner. The hosts were unable to make it count though, as a foul on McJannet gave Town a free kick.
The deadlock was broken moments later and it was the Mariners who took the lead. A high ball from McJannet was headed on by Green for COOK, who controlled it before firing low and hard past Morris from 18 yards.
Green and Amaluzor combined to clear another Hutton long throw, then Amaluzor saw the first yellow card of the afternoon for a foul on Lenni Cirino.
Five added minutes were played at the end of the first half and Little was booked for his protests after Kabia won the ball in defence and drew a foul.
No further chances came before the half-time whistle, with the Mariners holding a deserved advantage at the break.
SECOND HALF
No substitutions were made ahead of the restart and an early Hutton throw was eventually cleared by Kacurri, who also got to a Little cross first to head away from danger five minutes in.
Morris collected a low pull-back from Green as Town threatened for the first time since the interval, then a fast break by the hosts led to a corner when a low cross was blocked by Kacurri. Little’s delivery broke for McCleary but his driven cross was cleared.
The hosts continued to apply pressure and they drew level with 56 minutes on the clock. Little played a great cross-field ball for McCLEARY and after the winger’s first touch took him into the box, his second was a chipped finish past Smith at the near post.
Hale missed the target from inside the box as Gillingham aimed to complete the turnaround, then neat link-up play between Walker and Amaluzor looked to have created an opening at the other end but McCleary got back to clear for a throw-in.
A foul by Walker on Nelson Khumbeni gave the home side a free kick on their left on 64 minutes, although Seb Palmer-Houlden could only head Max Clark’s delivery over Smith’s bar.
Turi replaced Walker in Town’s first change soon afterwards, then Cook and Kabia both saw shots blocked in quick succession, with the latter superbly denied from six yards by Masterson.
After Gillingham’s strong start to the second half, the Mariners were now back in control of possession as they aimed to regain the advantage.
The hosts had a chance when McCleary ran onto a ball from Clark but he lifted it across goal and wide, with Smith racing off his line to narrow the angle.
Seconds later, they were made to pay for that miss as the Mariners got themselves back in front. Morris came off his line to meet a long, cross-field ball from Amaluzor at the edge of the penalty area but his touch presented KABIA with an open goal to tap into and reach 20 for the season in all competitions.
Kabia made way for Vernam after the goal as Town made a triple-substitution which also saw Burns and Sweeney come on for Amaluzor and Staunton.
Vernam almost had an instant chance to extend the visitors’ lead as Green played a low cross to the far post but Hutton got to the ball first to clear for a corner.
Sam Vokes and Bradley Dack replaced Masterson and Cirino as Gillingham made a double-change with 11 minutes to go.
But Town were now firmly on top and after Vernam cut inside from the left to win another corner, his flag-kick was met at the near post by GREEN to flick a header across goal and into the net for 3-1.
The Mariners went on to add a fourth goal with five minutes to go, as a great move saw Cook find Green on the right and he played the ball across the six-yard line for VERNAM, who made no mistake as he swept it into the net at the far post.
Warren replaced Oduor in Town’s final substitution, with Travis Akomeah and Harry Waldock coming on for McCleary and Khumbeni in the blue of Gillingham at the same time.
The hosts were looking for a second consolation goal as the game moved into at least six added minutes and Smith had to tip the ball over his bar after Clark let fly from distance.
Town continued to attack and after Hale was booked for a foul, Turi had an opportunity to make it 5-1 from the edge of the box but saw his side-footed shot blocked.
Vernam was just wide as the away side went forward again but that proved to be the final chance of the afternoon as the Mariners saw out the remainder of the game to secure a comfortable victory.
The result means Town now have an opportunity to move above Chesterfield and into the division’s top seven if they can win their game in hand, which comes when they travel to third-placed Cambridge United on Tuesday.
Town: Smith, Rodgers, Kacurri, McJannet, Staunton (Sweeney, 76), Walker (Turi, 66), Amaluzor (Burns, 76), Green, Oduor (Warren, 87), Kabia (Vernam, 76), Cook
Subs not used: Pym, Booth
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