The top two both picked up maximum points in the Lincs ECB Premier this weekend.
Ben Wright struck an unbeaten century as leaders Bourne defeated visitors Louth by 220 runs at Abbey Lawn.
Wright (104 no) and Peter Morgan (59 no) helped the hosts to 284 for 4,
Sebastian Darke took two wickets but his Louth side were dismissed for 64.
Jack Berry and Colin Cheer claimed three victims apiece while Jason Collinson (16) and Darke (14) top scored for Louth.
Grantham remain 35 points behind Bourne with three games to go after the weekend's seven wicket success against basement side Woodhall Spa.
Jay Parmar scored 26 runs as the visitors were dismissed for 101, Mark Footitt and Mason Hildrith the pick of the bowlers with three wickets each.
Grantham took 18 overs to reach victory, Ross Carnelley (42) leading the way.
Third-placed Sleaford were beaten at seventh-place Market Deeping.
Thomas Willoughby hit 50 as Sleaford posted 176, Deeping going on to reach 178 for 7 in the 38th over.
Hayatullah Niazi (39 no), Josh Smith (37) and Connor Gillett (33) scored well for Deeping as Willoughby took four wickets.
Lindum left Boston with a 209-run success.
Robert Cook (83) top scored as Lindum posted 300 for 8, Patrick Turner taking three wickets for the Mayflower men.
In response, Boston were all out for 91, Jonny Cheer making 29.
William Wright and Thomas Marshall both took three wickets.
Bracebridge Heath, in fourth, closed the gap on Sleaford after beating second bottom Scunthorpe Town.
Alex Moor took four wickets as Scunthorpe were out for 143.
But Bracebridge were made to work for victory, reaching 147 for 9.
David Whaplington top scored with 34, Thomas Giles taking four wickets.
RESULTS: Boston 91 Lindum 300-8; Bourne 284-4 Louth 64 ao; Bracebridge Heath 147-9 Scunthorpe Town 143 ao; Grantham 102-3 Woodhall Spa 101 ao; Market Deeping 178-7 Sleaford 176 ao.