The win snapped a five-game road losing streak for the Blackbirds (15-13, 11-6 Northeast Conference).
FDU (7-22, 6-11 NEC) jumped out to a 9-2 lead on a pair of 3-pointers and a three-point play, before the Long Island offense kicked into gear.
Wisseh gave the Blackbirds their first lead of the night with a 3-pointer to make it 14-12 at the 14:13 mark.
LIU never trailed again, shooting 56 percent from the field in the first half. LIU extended the lead to 44-28 before the Knights rattled off seven straight, including a 3-pointer by Sam Fernley just before the intermission.
The Blackbirds picked up where they left off in the second half as Johnson scored five straight and Julian Boyd tacked on a pair of foul shots to push the lead to 51-35.