Bet the turn scare card?
 

Villian is 51/2/2.5 over ~300 hands. Tends to call a lot on the flop and gets more aggressive on the turn and river. On the turn there's $28 in the pot and he's got $40 behind.

iPoker No-Limit Texas Hold'em (NL100), $1.00 BB (5 handed) SilverKitty Hand History converter by www.pokeronline.com.ua

Button ($123.35)
SB($52.45)
BB ($61.5)
Hero($107.1)
CO ($146.05)

SB: Post SB $0.50
BB: Post BB $1.00

Preflop:
Hero is MP3 with 9[img]/images/graemlins/heart.gif[/img], 9[img]/images/graemlins/diamond.gif[/img]
<font color="#CC2222">Hero Raise $4</font>
<font color="#666666">2 folds</font>
SB Call $3.5
BB Call $3

Flop:($12) 4[img]/images/graemlins/diamond.gif[/img], J[img]/images/graemlins/club.gif[/img], 3[img]/images/graemlins/diamond.gif[/img]<font color="#0030DD">(3 players)</font>
SB Check
BB Check
<font color="#CC2222">Hero Bet $8</font>
SB Call $8
<font color="#666666">1 folds</font>

Turn:($28) A[img]/images/graemlins/diamond.gif[/img]<font color="#0030DD">(2 players)</font>
SB Check
Hero...?