Danny Mandriou (penalty), Jaden Brown and Reece Hackett fired the Imps into an unassailable 3-0 lead before the match suffered a 15-minute suspension as rain, wind and lightning battered the Jakemans Community Stadium.
The match resumed and no further goals were added before half-time - but Mandriou, Ben House, Charley Kendall and Hayden Cann added further strikes for the visitors in the second period.
United (3-5-2): Cameron Gregory (Jake Lovelace 63); Tom Leak (Trialist A 63), Michael Bostwick (Will Hall 63), Brad Nicholson (Trialist B 63); Zak Mills (Trialist C 63), Keaton Ward (Sam Essien 63), Jordan Richards (Tom Edge 63), Martin Woods (Sam McLintock 63), Ethan Sephton (Ryan Hand 46); Kelsey Mooney (Oliver Wilson 63), Michael Gyasi (Keziah Martin 46).
Referee: James Bell.
Attendance: 1,514 (593 visitors).
PIC: Russell Dossett.