Better check your cruise contract. Mine clearly states that there is a luggage limit of 200# per person. I never noticed it until today when I was filling out my credit card info for my charge account.
Under clauses in Cruise Ticket Contract:
2. (a) Each adult Passenger is permitted to carry up to two hundred pounds (200 lbs.) of luggage aboard Vessel.
This is for Celebrity. You might want to check with your cruise company to see what their policy is.