How long should I allow to get from Miami port to Fort Lauderdale FL?

I am taking a Cruise from Miami port and flying out of Fort Lauder dale airport, what I need to know is if the boat docks at 8:00 am in Miami and I have to get thru security and take a taxi to Fort Lauder dale airport, what is a safe time to make my flight going out of Fort Lauder dale. I have it booked for 7:00 p.m. but if there is anyway an earlier flight will work can someone let me know? there is a 1:00 pm flight and a 3:00 pm flight also, would I have time to make either of these? I am not sure how big the FOrt Lauder dale airport is?