River bluff CR on doublepaired board

[ElSapo]

One early limper who has only been at the table 20~ hands, I complete in the SB with 76o, BB checks.

Flop is 245r, I check, BB checks, limper bets, I call, BB folds.

Turn is a 2, check-check

River is a 5, I checkraise.

I don't know much about the guy after 20 hands, but my logic was that if he has an ace, or maybe a king, he's calling if I simply stab at the pot, but check-check and then a bet on the river screams he doesn't have much at all... Of course, betting the flop maybe was better, or not completing in the first place.

Basic question is, pot has 3.25 BB in it after the river action is back to me — risk 2 to win it?