You won't be able to post pics until you pass 5 posts. We'll get you there.
OK, below is a pic of your disconnect. It is normally wired downstream from a main panel to power an outside air conditioner or hot tub. The breaker protects the wiring and also provides a handy shutoff close to the appliance.
By "inlet" do you mean the exterior receptacle where your extension cord from shore power plugs in to power the bus?
I'm imagining your electrical system as something like this:
Shore power (SP) panel > 50 amp extension cord between the SP panel and the bus > the 50 amp disconnect > the bus 100 amp main panel > your bus appliances/receptacles.
You normally wouldn't need a disconnect between the SP panel and your main panel so I may be imagining the disconnect in the wrong position.
Once we've got a good idea of what you've got and what you're trying to accomplish we can try to answer your questions.