marinas are notoriously noisy anyway, so I turn off the AC when testing at the dock. I'm mostly working to improve comms when on the hook or underway. BTW I may have similar equipment to you. The Mastervolt is 50 amp with a high amp output for the housebank and something like 1.5 amps for the start bank. If you have a unit that sounds about like this, I can pass along some caveats from my experience. I'm mostly satisfied but there are some potential gotchas.