Fifth-placed Sleaford CC became the first side to claim the scalp of Lincs ECB Premier leaders Bourne this summer, following an 89-run victory at London Road.
Thomas Shorthouse (49) and Drew Harbron (33) helped the hosts to 237 before they were dismissed in the final over.
Cameron Hall then claimed four wickets for the loss of 17 runs as Bourne were all out for 148, Tom Dixon's unbeaten 52 the visitors' top score.
Grantham closed to gap to 18 points with an eight wicket victory at second-bottom Market Deeping.
Former Notts man Mark Footitt took six wickets as Deeping were dismissed for 111.
Ben Coddington top scored with 44 as Grantham reached 112 for 2 in the 24th over.
Seventh-placed Boston were beaten by third-place Bracebridge Heath in the Lincs ECB Premier on Saturday.
Jonny Cheer's 87 - backed up by Rowan Evans (51) and Tom Bacter (37) - helped the Mayflower men to 206 for 6.
However, the Lincoln-based side made it to 207 for 6 in the 40th over with half centuries from Angelo Jayasinghe (67) and Vikram Atri (54).
Jack Tetther took two Bracebridge wickets.
Louth Town remain second bottom of the Lincs ECB Premier following a 37-run home defeat to Scunthorpe Town.
Jason Collinson took five wickets as Town finished their 50 overs on 208 for 9, Ian Snowden top scoring with 45.
However, in response Louth were all out for 171.
Colinson (43) led the batting with support from Sebastian Darke (36) as Joshua Knapton took six wickets for the loss of 34 runs.
William Wright's unbeaten 107 proved the difference as Lincs ECB Premier basement boys Woodhall Spa were beaten by Lindum.
Pranav Pothula added 71 runs as the hosts reached 215 for 2 to secure an eight wicket victory.
Tom White (61 no), Jay Parmar (40) and Tom Caswell (38) helped Woodhall to an earlier total of 213 for 8.
Lincs ECB Premier: Boston 206-6, Bracebridge Heath 207-6; Lindum 215-2, Woodhall Spa 213-8; Louth 171 Scunthorpe Town 208-9; Market Deeping 111, Grantham CC 112-2; Sleaford 237, Bourne 148.