You gotta think that transom is designed to handle 200 HP under any conditions. They'll have built it so that it can withstand that kind of pressure without any problem. Outboards are rated within a 10% margain so a 200 could conceivably be 220, and a 225 could be 205, also how often do you run above 5000 RPM anyway? So the only 2 problems I see are buoyancy, and insurance. The former should not be affected by the weight of the 25 extra ponies won't be much. Insurance is where I would watch out. It might not be a problem, it might cause them to deny a claim, those slimy [NSFW] will do anything to not have to pay. I would make sure to declare that beforehand, and make sure they know it's overpowered to be assured they won't pull a fast one on you when push comes to shove.