No. The gratuities are added to your onboard account daily and your total shipboard account is posted to the card you registered on the last day of the cruise.
What you can do is call Princess and ask to buy some OBC for yourself in the amount of the gratuities (or any other amount). Then when you start your cruise it's like they are prepaid. We started off our last cruise with a $325 OBC and most of that was prebought by us. Sure helped on the final day so we didn't have a heart attack at our final total.