Should I have bet this river?

[checkmate36]

Party Poker 0.50/1 Hold'em (9 handed) converter

Preflop: Hero is MP2 with 9[img]/images/graemlins/spade.gif[/img], 9[img]/images/graemlins/heart.gif[/img].
<font color="#666666">2 folds</font>, MP1 calls, <font color="#CC3333">Hero raises</font>, <font color="#666666">4 folds</font>, BB calls, MP1 calls.

MP1 is a fish from my buddy list. I have the perfect seat at the table IMO.

Flop: (6.50 SB) 5[img]/images/graemlins/club.gif[/img], 6[img]/images/graemlins/diamond.gif[/img], 8[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
BB checks, <font color="#CC3333">MP1 bets</font>, <font color="#CC3333">Hero raises</font>, BB folds, MP1 calls.

Turn: (5.25 BB) K[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
MP1 checks, <font color="#CC3333">Hero bets</font>, MP1 calls.

River: (7.25 BB) K[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
MP1 checks, Hero checks.

He probably doesn't have a K when the 2nd one hits but I took the showdown. SSH says bet marginal hands for value vs loose players. I couldn't pull the trigger. [img]/images/graemlins/blush.gif[/img]

Final Pot: 7.25 BB