The 240VAC/50Hz mains in Australia
is not compatible with 120VAC/60Hz systems on your boat without some manipulation of the incoming power.
The 240VAC can be stepped down to a nominal 120VAC with a transformer. The frequency mismatch is a separate issue altogether. If the equipment
onboard is truly universal with nameplates that state 100VAC/120VAC, 50Hz/60Hz then you only need to ensure that you have sufficient taps on the transformer to drop the voltage out of the transformer down to 100VAC and your "universal" equipment
will run happily.
If that scheme won't work, then you can look at using a universal voltage battery charger
to charge your house bank and run all of your US, 120VAC/60Hz equipment off of a properly sized inverter
DO NOT, under any circumstances, simply provide the 240VAC/50Hz shore power
to your vessel's AC system as every 120VAC piece of equipment subjected to this over voltage condition will dramatically fail.