$250ish behind, Hero has 6h7h in hijack...limped to hero, would usually raise here but limp goes to flop 5 ways. Flop comes 4h-5c-2s...MP bets out $5 and everyone calls including myself. Turn 7d...checked to me and I'm last to act and now with top pair still open ended...I just felt like this was a great place to stab at it with the lack of interest, tp, and still the draw so semibluff out $25 into the ~$35 pot, only BB calls. River bricks and BB leads out $20...hero???
I wouldn't even call the turn bet a semi-bluff. IMO, you are betting here for value and should expect to get called by a lot of inferior pairs with straight draws.
As for the river vs an unknown, this is a trivial call. You only have to have the best hand a small percentage of the time for this to be a profitable call.