Opponent is a little loose-passive and not very good overall. River play?

PokerStars No-Limit Hold'em, $4 BB (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

saw flop|saw showdown

SB ($163)
BB ($400)
UTG ($304.85)
Hero ($394)
Button ($372.60)

Preflop: Hero is MP with 6, 7.
UTG raises to $12, Hero calls $12, Button calls $12, SB calls $10, 1 fold.

Flop: ($52) 8, 5, 6 (4 players)
SB checks, UTG bets $32, Hero calls $32, Button folds, SB folds.

Turn: ($116) 7 (2 players)
UTG checks, Hero bets $80, UTG calls $80.

River: ($276) 8 (2 players)
UTG checks, Hero ???