Port Vale cemented their place in the top six and left Grimsby fans calling for manager Paul Groves to be sacked.
Andreas Lipa drove through a crowd of
players from the edge of the box for the opener, while Sam Collins scored a blistering 20-yard volley.
Marc Bridge-Wilkinson's superbly judged chip made it three, before Phil Jevons volleyed Grimsby back into contention.
Billy Paynter prodded home Vale's fourth and
Bridge-Wilkinson's 25-yard drive completed the rout late on.
Port Vale: Brain, Cummins, Pilkington, Collins, Brisco,
Bridge-Wilkinson, Lipa, Boyd, Paynter, Brooker, McPhee. Subs:
Delaney, Rowland, Armstrong, Littlejohn, Burns.
Grimsby: Davison, McDermott, Ford, Edwards, Crowe, Anderson,
Daws, Groves, Jevons, Onuora, Mansaram. Subs: Young, Rowan,
Hamilton, Hockless, Soames.
Referee: A Kaye (W Yorkshire).