We usually take a shorter path with our 4'3" draft. After an excellent anchorage in Little Shark River you can pass by Schooner Bank & pass through Yacht Channel to arrive at the 65' fixed bridge at Long Key and Lower Matecumbe. From here you can choose the Bayside or Hawk's Channel to Miami. This will bypass Marathon and shorten your route by about fifty miles. 'take care and joy, Aythya crew
Using Opencpn, I just plotted from Gordon pass in Naples, FL to the same point in the Hawk Channel going under 7 mile bridge (west of Marathon) or using the Yacht Channel going under the bridge at Channel 5. The distance via Marathon is 123 nm and using the Yacht Channel is 102 nm.