Mike Edwards was a doubt for the game with illness but was named in the starting eleven.
Blackpool boss Steve McMahon resisted the temptation to bring striker John Murphy back into the starting line-up after his recent return from injury.
For most the game the Seasiders showed their dominance with Richie Wellens and Neil Danns running the midfield.
Aidan Davison was busy throughout with fine saves in the opening 20 minutes from Mike Sheron and Wellens.
Town's first real chance fell to Jason Crowe. The former Pompey man was played in after clever work from Onoura and Boulding. Crowe's shot on the run was never going to trouble Lee Jones in the Blackpool goal though.
Before the break Sheron almost gave his team the lead, Town failed to clear a corner and the former Barnsley striker looked certain to score before Tony Crane flew himself in the way to clear.
At the break Edwards, still suffering from sickness, was replaced by youngster Greg Young for only his second league apperance.
Early on in the second half Michael Boulding was presented with a good chance to open the scoring. In space and with time, Boulding failed to control the ball before losing control and possession.
Davison was soon back in action with a finger-tip save to deny Wellens and then moments later another good save from Simon Grayson.
Town's breaks were few and far between but they did look promising. Boulding used his pace to break away before his low cross found Nick Daws. The loanee fired goalwards only for Jones to push the ball around the post.
From the corner came Town's goal. Onuora used his experience to flick the ball back into the danger area allowing Crane to slam home the ball from close range. With 19 minutes to go, Town needed to be solid at the back.
Davison was equal to the best that that Blackpool attack could offer as Young and Crane provided a solid barrier in front of him. Boulding should have helped seal the win late on when on the break. Using his pace well, Boulding got away from his men but his delivery into the middle was poor as Onoura and Campbell stood waiting.
In the final minute Darren Mansaram came on for Boulding, another sign that Phil Jevons has a lot to do before impressing Paul Groves.
Blackpool: Jones, Grayson, Clarke, Davis, Coid, Douglas, Wellens, Danns, Southern, Sheron, Taylor. Subs: Barnes, Hilton, Murphy, Bullock, Doherty.
Grimsby: Davison, McDermott, Crane, Edwards, Barnard, Crowe, Hamilton, Daws, Campbell, Onuora, Boulding. Subs: Young, Bolder, Hockless, Mansaram, Jevons.
League Table