What are the pro-cons using a combined solar/inverter/charger vs separated solar + inverter/charger in a marine application?
Also I have a 12V system today and I could also see that the new versions of the inverter/charges build on 24/48V systems. Is the recommended way to build a 24/48V battery storage and use a 12V DC-DC to supply loads?
IMO it depends for example on size of your ship/boat, where you're going to sail and how much failsafe you want.
Smaller boats usually have 12V system pre-installed. The bigger you go, the longer the cables and the longer the cables, the thicker they have to be to minimise cable losses. At that point 24V or even 48V systems come into play because they allow for thinner cables.
Upgrading from 12V to 24V requires some extra devices like DC-DC converters to step down from 24V to 12V to drive your 12V loads.
For your initial question about combined inverter/charger/MPPT in one box or separated devices: in a marine environment I would prefer separated devices. If one of the devices fail, it doesn't affect the whole system immediately.
Regarding 12V system, the boat is built in 1973 and at that time the amount of electronics didn't require more than a 12V system. 12V loads start to add up thus would make sense to have storage, inverter, solar on at least 24V to keep currents down. Starter and generators are 12V so either stick with 12V or if possible to run some kind of mixed system. Haven't seen a neat system implementation for a mixed solution.
