Having had both set ups I wouldnât swap back to the manual type after having a vetus electric one. If used properly they shouldnât use that much more water than manual ones (eco for small jobs, normal for big jobs and an empty the bowl without flush option)
I canât see how you could fill a tank in 2 days unless the tank hadnât been emptied properly or more likely an over sensitive gauge. Also would be interesting to see how big the tanks are on that boat.
John