I'm puzzled! Inland waterway boats are much better suited to having a big solar system than are sailing yachts. Boaters all have the same basic problem. You have proper power and hot water only if you run the engine or are connected to shore power.
Most sailing boats have some kind of solar installation although space is limited and the marine environment deeply hostile. Inland waters boats seem less keen, yet a 40 foot narrowboat can probably fit 20 x 150w semi-flexible panels on the roof at modest cost. Add a new generation inverter/controller and you can run everything except the heating in winter. You can even heat the water in your tank. The big question of course is battery storage.
We like Lithium. They tolerate a regular 50% discharge without any damage, and an occasional 80%. So you need at least 2 1/2 times as much nominal lead/acid power as you do for lithium, and maybe 4 times as much. Lithium also lasts much longer.
We are looking into sourcing Tesla battery packs salvaged from damaged cars. They would provide a wonderful solution to our storage needs.