6.50$ Turbo: TwoPair, river bet?

[marsus]

Hi,

PokerStars Tournament, Big Blind is t20 (7 handed) Converter on pregopoker.com

UTG (t2800)
UTG+1 (t1500)
MP1 (t1470)
CO (t1480)
Button (t3160)
SB (t1590)
Hero (t1500)

Preflop: Hero is in BB with K[img]/images/graemlins/heart.gif[/img] 3[img]/images/graemlins/club.gif[/img]
UTG calls t20, UTG+1 calls t20, MP1 calls t20, <font color="gray">CO folds</font>, <font color="gray">Button folds</font>, SB calls t10, Hero checks

Flop: (t100) K[img]/images/graemlins/club.gif[/img] 3[img]/images/graemlins/diamond.gif[/img] Q[img]/images/graemlins/club.gif[/img] (5 players)
SB checks, <font color="red">Hero bets t100</font>, UTG calls t100, <font color="gray">UTG+1 folds</font>, <font color="gray">MP1 folds</font>, <font color="gray">SB folds</font>

Turn: (t300) J[img]/images/graemlins/spade.gif[/img] (2 players)
<font color="red">Hero bets t300</font>, UTG calls t300

River: (t900) 8[img]/images/graemlins/heart.gif[/img] (2 players)
Hero checks, UTG checks

no reads.
Do i have to bet the river? And if yes how much?
I didnt bet because i had no idea what my oppenent has. Perhaps he was on a flush draw and didnt get it, so he wouldn't call me anyway. But now when i review it, i think it might be possible that he had a weak K or even a Q with what he would call a river bet given his play so far.