I believe that Tower Isle is approximately 2 hours from MoBay, in the opposite direction of CSA in Negril. The trip to CSA is approximately 1 hour 10 minutes. Cabs may make it in a little less time but it would still be a long trip, IMO.
My husband and I traveled from CTI to CN last September and if I remember correctly, it took about 4 hours. We had a really good driver though, he stopped once for us to visit the Del Sol shop in Ocho Rios and then again just after passing the airport for a stretch.