The Pilgrims, playing their second match inside 48 hours, drew 1-1 at Chesterfield in their final away fixture of the season.
United’s under-19s will conclude their campaign at home to Farsley Celtic on Wednesday.
Boston: Zach Biggs, Rueben Fogg, Josh Doran, Will Langford, Finley Ging, Ellis Perry-Burdett, Ezra Aaron, Kris Zaluzinskis, Nathan Bowen, Lucas Turrell (Jake Henderson 60), Luke Horne (Dexter Tomlinson 55). Sub (not used): JJ Ward.