Does your ship leave at 4 or 5? Once you land, hopefully with no delays, you then need to gather your luggage, and get transportation. You should be able to get to Miami, depending on traffic within 45- 60 minutes.
If your ship is a 4 o'clock departure, this is really tight. I would say, change flights, if you can..If it's 5, it would be better,and doable.
You need to get reliable transportation to get you there.Check out
SAS Transport Quality Shuttle Service at Affordable Prices
$15.00 pp each way. I have used them. Ask them about the time time frames.. Have fun!