Solid knocks from Paul Martin (20), Graham West (43) and Primosh Perera (37) had given Louth a decent start to 93-3.
But the hosts lost their last seven wickets for 51 runs to collapse to 144 all out as Ben Rolfs and Jake Benson each took four wickets.
Aidan Lockwood and Charlie Tomlinson brought up Lindum’s 50 off just 47 balls in an opening stand of 62 before both were out in quick succession to Andrew White (2 for 24 off 11 overs).
Perera then struck to leave the visitors 75-3, but skipper Robert Cook (40 not out) and Rolfs (31 not out) then saw Lindum home without further loss in just 36 overs.
On Saturday, Louth visit Grantham (noon start).