I got a 22 Velocity this weekend to replace my 24 Python that burned. The boat has a 1999 7.4 MPI fuel injected motor in it. I think around 310hp. I have the motor that came out of my python that was a 500hp 468 that had a 850 Demon carb on it. The carb cant be reused so I was wondering if this fuel injection system on this motor would work on my 500hp 468 with Dart rectangle port heads? If it won't work I guess I am looking for a 850 carb.

It can be made to work with some work and tuning shorten the lower runners and polish and port the upper Plenum. High flow air kit and tune from hardin marine should still be able to make.close to 500hp

put a good 850 carb on it and roll on...

Isn't the 7.4 310 an oval port motor? If so, you won't get it to work on the rectangular port heads.

Not worth the time, effort, or money. You will be further ahead to buy a stand alone system made for those HP levels like a Holley Commander.