You may be in for NEW mounting holes, so be prepared and seal the holes well!
If you use cable steering and it is old, I'd suggest replacing it now with a No FeedBack (NFB) system by Uflex or other. I just went from a 40hp to a 60hp (boat's rating) and the old steering that was fine w/ the 40 now tears the wheel out of my hands at speed. So I adjusted the fin above the prop to account for this ... now running at speed is fine, but if I let the wheel go at lower speeds, the motor torque turns the boat. Replace it NOW if you can ... you'll thank me!
Make sure your seats or seat bases are sound, as you will be flying w/ 60 ponies behind you! Chrckout the new pressed-aluminum 4-blade props from Turning Point, I get acceleration throughout the entire RPM range.