I originally put a 570 exider in my home built 6x6. You can see the build pix here.
Joie's 6x6 Toy
I ran that set up for maybe 60 min. before I was convinced that it was way too much motor. The snow mobile cluch didn't come in till 5000 rpm, and when it did, it was stupid fast. It would have been fun on a frozen lake or the sand dunes. But I wanted it for the woods. So I swapped it out for a 22hp Kohler. I still have the Yamaha setup with motor mount and stinger pipe if some one else would like to try it.