ahaha ! lol Dudes it's only 7.3 miles! After you exit the channel if you use the formula
T= D/S. Where D = 7.3 miles & S= 40MPH aprox then t= 10.95 so technically speaking Steel on the run&gun @ 55MPH you would make it in almost 8min.
Also I ment Sand cut even though for me Elliot Key is less thank 2 blocks from that since I cut through it

@ almost full speed
PS: Don't underestimate the power of the MERC! there not #1 in the water for no reason !