9.9 to 15 conversion.

[Paul.v]

I recently picked up a 9.9 Yamaha model 9.9SH 682C s 072228 in Ontario, Canada.
I was told it is an 89 but found its an 87 .
What I would like to do is buy what is required to upgrade this to 15 hp which I have heard is only a reed cage or restrictor plate & main jet.. I have a friend who runs circles around all the 15 mercs out there..
Is this feasable?
What parts do I need?
Thanks!
Paul

[boats.net]

I'm not sure we don't modify horsepower and never tried it.