The Pilgrims were beaten 4-0 at Mill Farm as the impressive Coasters wrapped up a league double over Lee Mitchell's side.
The main plus point of United's afternoon was the return of full-back Nathan Stevens as a second half substitute, following a long injury lay-off.
Boston (4-4-2): Jake Frestle; James Mallender, Harry Cranfield, Brogan Horniman, Joe Hardstaff; Jamie Gaukroger, Finlay Armond, Will Jackson, Ashton Taylor; Jack Bastow (Nathan Stevens 70), Xander Crashley.