Most Iso transformers can be tapped and switched to boost voltage. One thing that was attractive and that I was very grateful for on my boat was the PO's installation of Charles Iso Boost transformers. Not an economy solution, but made things very easy, a no brainer vs a manual system which has to be actively monitored and managed.
Marine: Isolation and Boosting Transformers
Charles now also makes an add on auto boost unit for standard 50A transformers.
Marine: Smartboost AC Transformer Booster