I don't like calling OOT. If he has an unlikely JT, is playing it tricky (like QQ or KK), because there is no reason he would bet it due the previous action, he has just to wait for you to bet again. Best scenario for him he has Two pairs, like AQ or AJ, or a crushingly lucky 77. So, I would raise large on the turn, make him to take a decision for his chips. Most of the time you are good in this spot.
At the river, he has a bluff, AJ or 77.
So, what happened?
Edit: I hate the questioners "How much are you playing with?". Count, MFaQrs, count!