The Pilgrims were beaten 4-1 at league leaders Guiseley, with Han Stevens netting United’s consolation.
Josh Stones bagged a hat-trick for the Lions, with Alex Mather also on target.
Boston (3-4-2-1): Charlie Wilkinson; Bailey Dilley, Owen Sheriff, Ben Robson; Elliot Foster, Haydn Tear, Mackenzie Burdass, Zane Millar; Finlay Armond, Ben Johnson; Sam Harris. Subs (used): Logan Tate, Joe Melson, Han Stevens, Krisztian Gagyi; (unused): Taylor Jaine.
Referee: Giorgio Luongo.