I'm planning on putting a 787 into my 2002 GTI, what am I going to have to do with the MPEM. Will the 717 MPEM work, will I need a 787 MPEM, if so which one? The 787 is out of a 97 GTX.
Physically, yes any of the engines can be made to fit... but if you swap from a 720 to a larger engine... there is a bunch of fab work that will need to be done, as the motor mounts are different, and so is all the electronics.
IMO... unless you are doing a crazy swap, to build an 80 mph ski... it's not worth the time, effort and the $$$. Not to mention, the resale is going to be bad since people don't trust other people's work. With the swap proposed... you would be better off selling all the parts, and buying a ski with an 800 engine in it from the factory.