Re: Advice
I have a 94 5.8EFI in my Four Winns and, knock on wood, have had no problems with it for 13 years. Its true that several marine-safe EFI parts are no longer available. The SX Cobra drive is a good drive and it has turned into the Volvo SX drive and parts are not a problem in getting. All that said, if I was doing it all over, I would go with a Mercruiser, not because I think they are better, but because they are easier to get parts for. Resale on the Ford EFI powered boats would also be less if that matters to you.
As for inspecting it, ALL the money is in the back of the boat. Forget how nice and shiny the rest of it is. Do a compression check on all cylinders, run it on muffs (or in water if available) and check for water leaks that might indicate freeze damage. Check the drive oil for water contamination. You may not realize how easy it is to sell a freeze damaged boat to someone that doesnt know much about boats so please have a mechanic inspect it.