This hand is bugging me. My opponent had vpip of 18%, pfr of 5%, AF of 3.

Party Poker No-Limit Hold'em, $ Hero (9 handed)

saw flop|saw showdown

MP1 ($10.80)
MP2 ($24.39)
MP3 ($16.55)
CO ($82.85)
Button ($28.90)
SB ($48.85)
Hero ($55.90)
UTG ($45.24)
UTG+1 ($35.70)

Preflop: Hero is BB with , . SB posts a blind of $0.25.
1 fold, UTG+1 calls $0.50, 1 fold, MP2 calls $0.50, MP3 calls $0.50, CO calls $0.50, 1 fold, SB (poster) completes, Hero checks.

Flop: ($3) , , (6 players)
SB checks, Hero checks, UTG+1 checks, MP2 bets $2, MP3 folds, CO folds, SB folds, Hero calls $2, UTG+1 folds.

Turn: ($7) (2 players)
Hero checks, MP2 bets $3, Hero raises to $9, MP2 calls $6.

River: ($25) (2 players)
Hero bets $15, MP2 calls $12.89 (All-In).

Final Pot: $52.89

Results in white below:
Hero has 6d 8h (one pair, sevens).
MP2 has 6h 6c (two pair, sevens and sixes).
Outcome: MP2 wins $50.78. Hero wins $2.11.

I only tried this bluff because I was in the BB and my opponent seemed like a solid player. I put him on a medium pocket pair because I thought he would raise most other hands, so I thought the only hand he would go all the way with was 77 or 22. Did I do a good job of representing the 7? And, did I have any fold equity on the river? This bluff has worked well for me in the past, but it went all wrong this time. Does anyone else make a bluffs like this when they have nothing in the BB and the board looks like that?

Stealth

Yikes. I can't believe he called that, it looks exactly like a badly slowplayed 7. Personally I prefer to just check/raise the flop in this scenario since I feel that you're risking a bit too much by just calling there. A solid player can't call that turn check/raise without a huge read.

it actually looks like a really good bluff with one exception, I would always like to have an out, even a gutshot, to a win. You did have an 8 for a winner though.. I think you need to re-evaluate your read on your opponent. He is either much worse or much better than you think him to be.

In general I agree completely that you want to have an out when bluffing but if there is an exception it's paired flops. If you get action you're often drawing dead or slim anyway.