Hi Bridgevin, welcome to Cruise-Chat! Even if everything were to go perfectly, I doubt you'd make a 8:46 flight out of San Juan. You might try the self-debarkation, which normally will start around 7-7:30 am. You will have to be able to carry all of your own luggage off the ship and through customs. It's still cutting it too close for comfort. If it were me, I'd change my flight out of San Juan.
Good luck and hope you have a marvelous cruise!