Once you have the boat, no house, no mortgage, no one to support, and especially no debt, the only variables would be unexpected repairs. You're independent and free. That sounds un-
American! You can budget within a few bucks what the other expenses will be: Normal boat maintenance (figure everything, from bottom paint to depreciation on stuff like engine and sails), food, entertainment, fuel, dockage/mooring fees, insurances, misc. This establishes a baseline that you can deviate from. If you plan your movements well, the prices of things are very predictable with all the info. now available. You can avoid the $25 burgers by just not going there. Without a good budget, costs could really get out of hand but doing one ahead of time can really give you the confidence to do it. Open a new Excel spreadsheet and lay it ALL out, month by month, a couple of years into the future. In reality 800k should yield a reliable and fairly safe 5%. That's 40k/yr. Plenty unless you go for the $25 burger every night.