600nl, pure bluff in the battle of the blinds

[evil_twin]

$600nl, full ring, I have $750, opponent just has me covered. Read is that oppenent is relatively passive, and is capable of laying down semi decent hands to strong action. I'm probably seen as solid, haven't done anything silly in this session yet.

I'm in the BB with 3[img]/images/graemlins/heart.gif[/img]Q[img]/images/graemlins/club.gif[/img]. All fold, SB completes, I check.

Flop: 9[img]/images/graemlins/heart.gif[/img] 6[img]/images/graemlins/spade.gif[/img] 7[img]/images/graemlins/spade.gif[/img]
SB checks, I bet $12, SB calls.

Turn: 8[img]/images/graemlins/spade.gif[/img]
SB bets $12, I bet $45, SB calls.

River: 10[img]/images/graemlins/heart.gif[/img]
SB checks, I bet $125.

Obviously I fold to a sensible sized bet on the turn. Am I a donk or is this fairly standard?