Hey Old Sailor 2, you must be and old sailor, somewhere around my age, 68. Anyway, you have to disassemble the cabinet next to the chart table, remove the bench seat base and then the one section of floor comes up and you need to remove the marine board under the refrig compressors. Then you need to dig out all the foam around the old aluminum tank so you can break it loose... of course you have to remove the tank fittings also. Once you get the tank loose, you can lift it out and take it out entry. Reverse for new tank and once it's in, refoam it to secure it and Wala your back in Bidness as they say in the south. Time consuming not that difficult,only need help when lifting out and setting in the new tank. If you get the new tank custom made from the company in Maine, you need to vent the water tank to the shower sump, the external vents need to be too high, they'll explain it to you.