Paul Simpson urged Carlisle fans to turn up the volume for the Cumbrians’ final push for automatic promotion.
First-half goals from Leeds loanee Alfie McCalmont and Jordan Gibson took Simpson’s side up to second in League Two.
And after a shaky opening half-hour they proved too strong for the Mariners, much changed from beating Southampton to reach the FA Cup quarter-finals for the first time since 1939.
Only four Town players kept their place in the starting line-up as manager Paul Hurst looked to freshen up his squad, with skipper Luke Waterfall and double penalty hero Gavan Holohan notable absentees.
“It was a tricky game,” agreed Simpson. “I didn’t know what to expect from Grimsby after the fantastic week they have had.
“I thought they had energy about them and we had to grind it out.
“For the first 30 minutes we didn’t show a lot of quality but we stayed with it.”
The home crowd was largely silent until McCalmont netted his second goal in three games after Alex Hunt was caught in possession.
A minute before the break Carlisle doubled their advantage as Jordan Gibson fired into the bottom corner of Max Crocombe’s net.
However, Grimsby were insistent referee Marc Edwards should have stopped the game because Hunt was down on halfway after a head knock.
It was tough on Town, who began brightly with Otis Khan shooting narrowly wide and George Lloyd forcing a big save from 6ft 9in keeper Tomas Holy.
“We have got to enjoy this because if we can’t enjoy this we have got problems,” said Simpson.
“I just sense they (the fans) are a bit nervous. I would ask them to make more noise and back us.
“I can’t criticise them and this can be a horrible place for away teams if we can get the crowd on their backs.
“Last February and certainly last summer no one expected us to be sat second with 34 games gone. We are in a good position and if we keep pushing each other on who knows where it might take us.”
Hurst said of Hunt’s injury: “Player safety is what I always hear.
“It was obvious it was a head injury. Alex had a big lump on his head so we are not making anything up.
“I had the fourth official stood beside me looking at it. I didn’t think it was a good enough performance all round but that’s not why we lost the game.”
On his new-look side, Hurst added: “I changed the team around and wanted to give people opportunity.
“Some almost had to play while there were one or two we needed to look after.
“Some were itching for an opportunity. But a lot in general made my job easier, I don’t feel like my job got harder.
“You don’t know when your chance is going to come but when it does you have got to be ready.
“Not for one minute do I think someone goes on the pitch not wanting to do well. But you have got to make it happen.”
Town were denied a late consolation when Lloyd’s header from Josh Emmanuel’s cross hit an upright.
Grimsby’s defeat dropped them one place to 17th but they are 12 points from the relegation zone and can largely concentrate on their last-eight FA Cup tie at Premier League Brighton.
