gonna get screwed i bet
If it is really trashed and it sounds like it is you will end up spending a lot more in parts than the boat will ever be worth. That said, you would need to check the records in Mexico to see if proper paper work was filed to sieze the boat for unpaid bills. If proper recored were filed then the marina or port facilities ended up owning the boat. You would need to find out who they sold the boat and follow the paper trail. Its not too hard to do that in the States, but I have no idea about how to do it in Mexico.