[mythrilfox]

Well, he can probably put you pretty squarely on a 7 here, since I don't see a set or two pair not putting in a raise somewhere before the river. We can probably rule out a complete bluff since he doesn't know if you're capable of laying down a 7 here.

So you are hoping for a split at best. On the end you are calling 400 to win 800, so you'd have to split...
x*400 - (1-x)*400 = 0
x=50% of the time (check my math)

It's pretty much a judgment call, then... like I said, a good player is going to know to push with a 7 here a lot, unless you've shown him a boat in the past on similar occasions, but if he's just decent he might be a little timid and tend to call with a straight here, especially in the heat of battle.

Plus his action up until the river makes a boat a little more likely, since his turn bet could very likely be a monster hand looking to price you in. Hands like 97 usually check behind, since he doesn't particularly want to priced off a weak made hand with outs to improve.

Also, did you consider leading the turn? I think it's going to be very hard to bluff raise you on the turn on this board... and hands like 9T will almost always just flat-call, giving you a chance to hit your draw. On this board, I would think if you get raised on the turn your outs aren't clean anyway (except for possibly a 7). Plus you get to protect your hand against overcards and you still have outs to improve against a 9 or an 8.