For under 8k it will be hard to find a go-anywhere boat, even with an exhausted
diesel. But south
Florida is full of fixer-uppers for sale--my first was one of those. I wouldn't consider owning a boat with an inboard diesel: who wants a big stinky machine in their living space? Both my boats (27' and 31') have had outboards, and they're initially far cheaper and always easier to maintain than diesels. Electric motors need electricity, and I doubt
solar panels and
wind noisemakers could keep up with the draw, so you'd need some kind of
motor to generate. At the end of the day, you can
cruise anywhere on almost any
budget, limited mostly by how much discomfort you can take.
Also, not all boats from the 70s/80s make good cruisers. Find the
hull shape you want or find acceptable and go from there. Everything else can be replaced, but you're pretty much stuck with the underwater profile with which the boat was built.