Combine first 6 ingredients. Pour half of mixture over crabs; cover and chill at least 1 hour.
Combine remaining marinade mixture, corn, and next 4 ingredients; cover and chill.
Remove crabs from marinade, discarding marinade. Grill crabs over medium-high heat (350° to 400°), without lid, 2 minutes on each side or until done. Serve hot or at room temperature with black bean salsa.