The #1 most common problem with boats is that people don't maintain them, so they break and then sit on the side of their house until the wife complains to get rid of the hunk of junk sitting on the side of the house... So it get's posted on CL for cheap...
If it's an AQ125, parts will be three times as expensive and likely much harder to find than your current nightmare...
So if it has been sitting for awhile it will likely need:
Fuel tank clean out
All new filters, fluids, oil and lubes
Basic tuneup
Carb rebuild
Outdrive impeller
After that, then you will have to fix what caused the boat to be parked in the first place... Engine knock, overheating, fluid leaks, oil leaks, basic electrical issues, charging system issues, steering issues, outdrive noises, etc...
Good luck...