Water maker advice?
Doug, you did say you''d welcome ''any advice''...
Given the tankage on a 40'' boat, you should be needing to make 5-10 gals per day, hardly the 40-50 you mentioned. *Especially* if you want a 12V maker; large motors put a big demand on even large 12V battery banks.
While not a ''rule'', I''ve found most boats have an imbalance in their ''energy equation'' (at least, while cruising) on the ''generation'' side. This means that, even with their 12V alternative energy sources (wind, solar), they still must occasionally generate power (run the engine or aux generator) rather than be looking for ways to consume add''l stored 12V energy. If your boat fits this description, why not install an engine-driven (either main or aux) water maker? To do so means you get ''free'' water while doing the mandatory batteru charge, anyway. Installing a 12V maker just imbalances the ''energy equation'' even further.