When larman said he had 50 amp shorepower, 95% of the time that means 50A/220/110V which is a four wire system with two hot legs of 110 to neutral, a neutral and a ground all providing 220V between the two hot legs.
A single 110V inverter (unless it is a two leg 220V one) can't handle two legs of 220V but it can handle one of the 110V legs. Amost all boats with 50A/220/110 power split the legs and feed two separate 110V busses on the main electrical panel. You just take one of those 110V legs that go to the panel, reroute it to the inverter's transfer switch and then feed the 110V inverter output back to the panel.
One caveat is that most 110V inverters have a 30A rated transfer switch. There should be a master breaker on the main panel for each leg. If it is 50A then replace it with a 30A one to protect the transfer switch from excessive current. That may limit what you can power from that leg. There is a solution but it gets too complicated to discuss here.
But if the OP isn't entirely comfortable with AC wiring, get a marine electrician to do it for you and determine exactly what kind of AC system you have.
David