Ryan Donaldson was the destroyer-in-chief as he netted a hat-trick for the Conference promotion-chasers. He handed Cambridge a 21st minute lead and added a fierce free-kick on 78 minutes and a driven penalty four minutes from time.
Donaldson was also inadvertently on target for the Pilgrims when he headed Netan Sansara's 67th minute corner into his own net. Cambridge's other goal was scored by Tom Elliott on 43 minutes.
Boston (4-3-3): Ashley Timms (Sam Vince 63); Peter Bore. Conor Marshall (Charlie Ward 78), Carl Piergianni, Netan Sansara; Ben Milnes, Gary Mills (Ian Ross 46), James Reed (Marc Newsham 46); Spencer Weir-Daley (Billy Bennett 46), Jordan Nuttell (Charley Sanders 46), Ben Fairclough (Ricky Miller 46).
Referee: Steve Ross