Yes, the majority of marine radars come with an HD transducer and cables. As for the mounting kit, it depends on the manufacturer and the model of your radar. Not all radars come with the same accessories upon purchase, this varies by brand and model.
Before purchasing, you should check what is included in the box. It should be indicated on the packaging whether a mounting kit is included and if it isn’t, it should say how you can purchase that separately. You can also check the product website to see what you’re getting and where to purchase all the parts you need for your radar.