Here are the full details. The boat was parked covered in my driveway for around three years. Just before storage, I had the lower unit rebuilt due to prop collision with rocks because the tilt was not operating properly. Prior to covering up, I did drain the block. As part of the process of getting it running again, I installed a new battery. It would not turn over at all. I got only a single click when turning the key. I changed out the starter solenoid and still had no results so I replaced the starter and then she turned over but would not fire. I then drained the old gas and filled it with new non-ethanol gas. Still no fire. I then replaced the spark plugs and the carburetor. Then when I attempted to crank she started to rotate and then seemed to lock up. I have attempted to turn the crankshaft by hand using the alternator pulley but all that happens is the belt slips. Tightened the belt but had no success. It still just slips. Prop turns freely even when in gear. I don't know another way to manually turn the engine because the front motor mount blocks access to the crankshaft pulley. I have considered pulling the valve cover and blasting it with lube but I'm not sure if I'm at that level yet. Could it be a stuck piston or valve or even a flywheel issue? Any advice is greatly appreciated.