$27: Limped behind and flopped big draw

[JayTee]

I don't know how I feel about this hand. Big stack has limped in a few times but not been raised or showed his hand down but did fold to a bet on a low card board. Is my limp behind OK? How do you play the flop?

PokerStars Tournament, Big Blind is t200 (5 handed) Converter on pregopoker.com

UTG (t4295)
Hero (t1845)
Button (t2410)
SB (t2070)
BB (t2880)

Preflop: Hero is in CO with 6[img]/images/graemlins/heart.gif[/img] A[img]/images/graemlins/heart.gif[/img]
UTG calls t200, Hero calls t200, <font color="gray">Button folds</font>, SB calls t100, BB checks

Flop: (t800) 9[img]/images/graemlins/heart.gif[/img] 7[img]/images/graemlins/heart.gif[/img] 8[img]/images/graemlins/spade.gif[/img] (4 players)
SB checks, BB checks, UTG checks, <font color="red">Hero bets t1645 (All-in)</font>