Opp is 50/0/3.8 over 40 hands. Should I raise the turn with 4 to a straight on board? As played, river is crying call, right?

Full Tilt Poker
No Limit Holdem Ring game
Blinds: $0.10/$0.25
7 players
Converter

Stack sizes:
UTG: $39
Hero: $22.85
MP1: $37
CO: $29.10
Button: $24.65
SB: $23.85
BB: $25.70

Pre-flop: (7 players) Hero is UTG+1 with 5 5
UTG calls, Hero calls, MP1 calls, 2 folds, SB calls, BB checks.

Flop: 4 6 2 ($1.25, 5 players)
SB checks, BB checks, UTG checks, Hero checks, MP1 checks.

Turn: 5 ($1.25, 5 players)
SB bets $1.25, 2 folds, Hero calls, MP1 folds.

River: A ($3.75, 2 players)
SB bets $3.75, Hero calls.