Macclesfield were also left biting their nails as one of the clutch of clubs who could be still be relegated next weekend.
The game exploded five minutes before half time when Grimsby's talented winger Mark Goodfellow beat his man before crossing perfectly for the burly Gary Jones to lean back and loop his header over the stranded Alan Fettis.
Macclesfield responded within two minutes. Paul Harsley battled his way to the by line before threading across through the defence for Marcus Richardson to head home from the six yard line, his first goal in seven games since joining on loan from Chester.
Earlier Steve Mildenhall had produced a stunning save to palm wide an Alan Navarro shot from 25 yards in the 13th minute. Grimsby should have scored in the 19th minute but giant centre back Rob Jones planted an eight yard header into the away crowd.
Macclesfield again went close in the 33rd minute when a curling drive by John Miles sailed inches past the post. Both sides had chances to steal the win in the second half. Macclesfield went close in the 60th minute when a twenty yard Harsley free kick clipped foot of the post.
Jones had a chance in the 62nd minute when he threw himself at Andy Parkinson's cross. Moments later Alan Fettis made a fine save 15 yards shot from Goodfellow.
In the closing stages Alan Fettis made a fine double save first blocking the drive from Curtis Woodhouse before grabbing the rebound from Gary Cohen.