Playing a monster OOP

[Hollywade]

Full Tilt No-Limit Hold'em, $0.50 BB (6 handed) Full Tilt Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Hero ($50.80)
BB ($70.85)
UTG ($118.95)
MP ($54.15)
CO ($54.25)
Button ($126.30)

Preflop: Hero is SB with 7[img]/images/graemlins/club.gif[/img], 7[img]/images/graemlins/spade.gif[/img].
<font color="#666666">2 folds</font>, <font color="#CC3333">CO raises to $1.75</font>, <font color="#666666">1 fold</font>, Hero calls $1.50, <font color="#666666">1 fold</font>.

Flop: ($4) 5[img]/images/graemlins/diamond.gif[/img], 7[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">CO bets $3</font>, Hero calls $3.

Turn: ($10) 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">CO bets $7.5</font>, Hero calls $7.50.

River: ($25) J[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $15</font>

This is yet another demonstration of why I hate being out of position. I'm obviously afraid of scaring the guy away. That's why I just called the flop and the turn. However, I'm not going to be caught with my pants down when the river goes check-check. I don't know this guy well enough to be confident that he will fire again.

How do you guys feel about my check-call, check-call, lead out way of playing this? How about the size of the river bet?

On the turn, I actually thought there was a good chance he had a pretty good hand. However, like I said, I wasn't sure if it was something he'd go to the felt with.

I did what I thought I should to get maximum value on the river.

Thoughts?