I would drain the fuel tank to not suck up any more bad fuel into the pump. Then I would install a new battery. Then I would put the key on the post and see if the fuel pump runs. If the fuel pump runs, then with the throttle fully depressed, wide open throttle (which disables the fuel injectors) I would see if the engine turns over for 5 seconds or so. If the engine turns over, then I would be comfortable to invest the time and money in replacing spark plugs, oil and filter, coolant, and 4 gallons of new fuel, and a 1/4 of a bottle of B12 Chemtool in the fuel tank to help clean up the fuel injectors. Then I would try to start it and go from there… hopefully it runs well and you can get it on the water for a real test. You will probably have some other things needed, maybe even replacing fuel injectors if it runs poorly, but that would be my approach.