I guess to cross an ocean or any place in the world. Range fuel is only one factor, other factors stability, water, food, heat and sanitation. The Eagle being a full displacement requires no stabilizing, holds 1200 gallons of diesel at 1200 to 1500 rpm which is 2 mpg, has 2 refrigerate and 2 freezers, a water maker that needs rebuilding, holds 400 gallons of water, a 5 kw cruise generater and plenty of storage for food. However the furthest we have been is 300 miles which is far enough.
True story.
When we first bought the boat the furthest long cruise for us was 30 miles Seattle to Everett. We sub rented on the commercial dock, which most cruised 24/7 to Alaska. Anyway I was so so glad to be tied to a dock, while thanking the commercial for helping docking. They enquired where we from I said Seattle. They burst out laughing, so long range is relative. 30 miles is still long for me.