2003 & 2004 250XS ECU's exchange with the 2005 250XS ECU's to get the 6400 Rpm's

Has anyone heard if this exchange of ECU’s can be done ? Would this exchange invalidate the warranty if a certified Mercury master technician did it? A lot of us who have the older 2004 or 2003 250XS would be interested in this possible exchange . I see no reason for this exchange not to be valid (i.e. warranty invalidated) on a 20-inch shaft version of the 250XS. All comments would be appreciated on this topic.:)

I was told the fuel curve also changed and that it would not be backward compatable. I have an 04 250XS, and would like to change mine.

Terry would changing the ECU's also change the fuel curve as well? Or do you have to program in a different fuel curve for the older 250XS then the 2005 250XS? I am new here to these boards and this whole process of swaping out ECU's is new to me as well.