I've got kind of a complicated question...any help would be great.

I have a 18ft pontoon boat with a 1990 9.9 Mariner Outboard. Ok, I know
what you're thinking, and no, it doesn't go very fast. The boat was
moored on a lake with a Horsepower restriction. So, I want a bigger
motor. I would like to purchase the 25HP Mercury that Academy Sports &
Outdoors sells
[http://www.academy.com/index.php?pag...arine&pgNum=2],
but I don't know if it will work (i.e. rigging, shaft length, etc).
Any Ideas?