When you purchase a fishfinder unit such as a humminbird 1197 do they normally come with everything you need to install and use the unit completely, or are cables and mounting equipment and different parts sold seperately. I know nothing about them so when I get ready to purchase a unit I want to make sure I have everything I will need to use the unit on a boat. Also, who is the cheapest place to buy humminbird 1197 units from or other units for that matter.