WiFi fallover to Verizon MIFi6620L

I have a new Pepwave surf on the Go on my sailboat and am using the marina WiFi to connect to an on-board wireless camera to monitor my boat systems while not on board.
The marina cut power today due to flooding and their WiFi signal went off and I thought I would fall over and connect to the MiFi as a WLAN signal. I am not at the boat, but was there earlier and my MiFi device had Verizon signal and is powered off my on-board inverter and boat house battery system.
I have the MiFi listed in a Profile with the log in information. I thought it would automatically search for one of the profiles and log on if the primary WiFi signal failed (or I moved my boat out of range). I bought it for this purpose as I cruise and visit multiple places and want to make sure I connect to marina WiFi and not my MiFi when in port. Did o get the right device to do this? Would it make a difference if I had a USB cellular antenna?
Thanks