Stamford Town were knocked off top spot as their title rivals took advantage of their games in hand in the South Lincolnshire and Border League on Saturday.
Town had a rest day but Boston and Billingborough both won with Boston taking over at the top with a slender three point lead ahead of Stamford with Billingborough just a further point behind.
Fourth-placed Bourne 2nd XI are just nine points off the lead but have played a game more than the top trio.
The next two weekends are crucial for the title contenders as Boston entertain Stamford on Saturday and Billingborough visit Uffington Road the following week.
In the last round of matches, Paul Deans’ five wickets - 35 for the season - were instrumental in Boston’s win over Sleaford 2nd XI while Luke Hollingworth took his runs total over the 300 mark with 68 in Billingborough’s victory over Lindum Ramblers.
Bourne 2nd made the day’s highest score of 257-6 as they beat Welby. Matt Creaney (81) and Jonny Murdoch (83) were chiefly responsible for the big score.
In Division One, Long Sutton’s lead stretched to 33 over Baston who went down to Friskney while Sutton overcame fourth placed Thomas Cook by three wickets.
Matt Cox of Billingborough 2nd XI was the division’s top wicket taker with six for 42 but he could not prevent his side going down to Spalding 2nd by 16 runs.
Premier Division - Sleaford 2nd 82 (Deans 5-10), Boston 86-5; Billingborough 159-6 (Hollingworth 68), Lindum 102; Bourne 2nd 257-6 (Creaney 81, Murdoch 83), Welby 120; Belton Park 103-9, Woodhall Spa 2nd 90; Skegness 2nd 116, Grantham 117-8.
Division One - Friskney 232-8 (Grant 51), Baston 130; Thomas Cook 164-8, Long Sutton 168-7 (A Wright 52); Blankney 108 (Braithwaite 5-21), Heckington 63; Spalding 2nd 190 (Klompas 62, Cox 6-42), Billingborough 2nd 174 (Stanley 65); Moulton Harrox 155, Boston 2nd 110.