Five years is a long time for an engine to be sitting idle--particularly if left with gasoline in the fuel system.
Battery's probably toast. Carburetor may be all gummed-up from the fuel turning to lacquer, so she might need a carburetor rebuild. The fuel probably should be pumped-out and discarded. Other than that, could be fine. You might want to consider hiring a qualified marine mechanic.
But if you want to go it alone... Hmmm...
New battery. Pump out and properly dispose of the old gasoline, put new in. Maybe change the oil and filter right off. (There are differing opinions on whether motor oil degrades just sitting there.) Replace the water pump impeller. (That will
certainly be done-for, after five years.) Remove all the spark plugs, spray a bit of oil in each cylinder (I might tend to use the fogging oil I use for winterizing), as the cylinder walls will be dry as a bone.
I think I got it all.
She might just start-up and run like a top

.
As for the rest of the boat: Should be fine if she's been sitting in a garage all these years. (Providing rodents haven't gotten in and destroyed the carpeting and upholstery, as sometimes happens.)
Jim