In a food processor combine the marinade ingredients. Process until fairly smooth, 20 to 30 seconds. Pour into a medium, nonreactive bowl and season with salt if desired. Add the shrimp and turn to coat. Cover and set aside at room temperature for at least 20 minutes but no longer than 30 minutes.
Prepare the grill for direct cooking over high heat (450° to 550°F).
Brush the cooking grates clean. Grill the shrimp over direct high heat, with the lid closed as much as possible, until the shrimp are firm to the touch, lightly charred, and just turning opaque in the center, 2 to 4 minutes, turning once or twice. Remove from the grill and serve right away with a squeeze of lime.