A maiden Lincolnshire ECB Premier League century for Dan Freeman and six wickets from Joe Peck boosted Grantham’s progress away from the relegation zone.
Peck was one of three bowlers to take six, Louth’s Amila Wettasinghe adding to Grimsby’s problems with his haul which Nick Goacher set the scene for Sleaford’s victory over Lindum.
Woodhall Spa opened up a 20 point lead at the top despite a slow start at home to Bourne.
Half centuries for Sam Evison and Ricky Lovelace took Woodhall’s final total to 248 for seven before Bourne were bowled out for 133 of which Tom Dixon hit 62.
Bracebridge Heath got their title challenge back on track after Paul Cook’s 88 helped them to 209 for six at Skegness who were all out for 117.
And Sleaford moved into third with a 10 wicket win over Lindum who were restricted to 155 for nine, Goacher taking six for 40.
Tim McIntosh (89no) and Tom Shorthouse (65 no) then saw their side to victory in 31 overs.
At the foot of the table, Spalding are now 30 points adrift with Grimsby Town, Skegness and Market Rasen above them, just 10 points separating these three.
Wettasinghe was instrumental in bowling Grimsby out for 94, a total Louth reached for the loss of three wickets while Market Rasen were all out for 141 in a much tighter game at home to Market Deeping.
Will Bradford hit 44 and Tom Boryszczuk 47 in Rasen’s innings and at 90 for three, the visitors looked comfortable.
However, Matt Rutherford’s dismissal of Ajaz Akhtar for 58 signalled a collapse to 116 for eight.
Tom Andrews and Pat Brown dug in to add 19 before Andrews fell to James Fussey and it was left to the final pair, Brown and Lee Peacock, to steer Deeping to the slenderest of victories.
Rutherford took four wickets and Boryszczuk claimed three.
Dan Freeman’s 122 came off 128 balls, helping Grantham to the day’s highest individual total of 295 for four, Rohan Nurse hitting an unbeaten 55.
Spalding lost an early wicket but Warren Nel (49) and Josh Newton (52) pushed the score along.
Both fell to Joe Peck whose six for 50 saw the visitors bowled out for 150.
Results: Grimsby 94 (Wettasinghe 6-28), Louth 95-3; Bracebridge Heath 209-6 (Cook 88), Skegness 117; Lindum 155-9 (Goacher 6-40), Sleaford 159-0 (McIntosh 89no, Shorthouse 65no); Market Rasen 141, Market Deeping 142-9 (Akhtar 58); Grantham 295-4 (Freeman 122, Nurse 55no), Spalding 150 (Newton 52, Peck 6-50); Woodhall Spa 248-7 (Evison 50 Lovelace 55), Bourne 133 (Dixon 62).