1+.20 18man possible semi-bluff

[ItalianFX]

These are from 1+.20 18man tourneys.

My opponent has been playing an average number of hands. He hasn't been doing anything stupid, but he's starting to annoy me.

Poker Stars
No Limit Holdem Tournament
Blinds: t50/t100
6 players
Converter

Stack sizes:
UTG: t4575
UTG+1: t3080
CO: t780
Button: t1595
SB: t3210
Hero: t2270

Pre-flop: (6 players) Hero is BB with 4[img]/images/graemlins/diamond.gif[/img] 7[img]/images/graemlins/heart.gif[/img]
3 folds, Button calls t100 <font color="aaaaaa">(pot was t150)</font>, SB calls t50 <font color="aaaaaa">(pot was t250)</font>, Hero checks.

Flop: 7[img]/images/graemlins/diamond.gif[/img] 6[img]/images/graemlins/spade.gif[/img] 3[img]/images/graemlins/spade.gif[/img] (t300, 3 players)
<font color="#cc0000">SB bets t300</font>, Hero ???

The more I thought about this, the more I thought it could be a flush draw semibluff. If I put someone on a hand like that, should I be raising here? If I raise and he calls, and the turn is a non spade, will I have to check the turn and give him a free river?