The Pilgrims accounted for Blyth Spartans, 3-2, on the Jakemans Community Stadium 3G pitch.
United's goals were scored by Finley Ging, Luca Alonzi (penalty) and Will Green.
Boston: Jake Lovelace (Zach Marsh 46), Billy Bradley, Oliver Nicholson, Will Langford (Jake Thompson 80), Finley Ging, Jacob Scott, James Owen, Harry Wood, Luca Alonzi, Charlie Burden-Whittleton (Rueben Fogg 87), Will Green (Rhys Smaller 90). Sub (not used): Sean Bray-Smith.
Referee: Istvan Mod.