My dad uses tracvision on his boat.
http://www.kvh.com/tracvision_kvh/ He used to use direct TV and just added another reciever from his house account. but obviously he coudl only use it when he was docked in his home slip.
The tracvision is pretty cool, but it's expensive.
Your best bet is just hook up a smaller LCD TV ( best viewing in bright rooms) and a good antenna and catch the games on broadcasted loacl channels ( ABC, NBC, ect)