I have about 15 Feral cats that live on my street. They do like to crash on my boat..... I do keep it covered. They haven't peed on the boat but one of those bastards did spray my trailer tire. There really isn't much you can do. You could call a local cat rescue...... They may be able to help you trap them for relocation. When I bought this house six years ago, there was an old lady that lived next door that used to feed all the cats. At that time, there were about 35-40 strays running around and reproducing. I called a cat rescue and they came out and trapped about 15 cats the first night. They neuter and then realease them. Some of the cats were put down due to having Mange or other communicable diseases. If you feed them, they'll never leave. I have heard that if you put down some Cayenne pepper it will discourage them from going to that area but I've never tried this myself.
On another note, cats will control rodent and insect population. I have a friend that had a Rat living in her garage. It chewed through the wiring Harness on her Lexus SUV. Toyota warranties don't cover Rats chewing through your wiring so it was an expensive repair. Toyota Service suggested she get a cat.