Played in front of 1,004 supporters, United raced into a three-goal lead courtesy of Jordan Preston on 12 minutes and a Danny Elliott brace in the 14th and 45th minutes.
United sealed the deal with second half strikes from Jordan Burrow (66) and Jake Wright (90) after Kyrell Wheatley had seen red from Premier League referee Kevin Friend following a horror challenge on Luke Shiels.
Boston (4-3-3): Peter Crook (Josh Barnes 46); Matt Tootle (Jay Rollins 78), Luke Shiels (Trialist A 55), Scott Garner, Scott Duxbury; Paul Green (Jordan Burrow 46). Tom Platt, Shane Byrne (Connor Dimaio 70); Fraser Preston (Terry Hawkridge 46), Danny Elliott (Jake Wright 64), Jordan Preston (Joe Leesley 46).
Referee: Kevin Friend.
Attendance: 1,004 (217 visitors).
PIC: Russell Dossett.