How do you change 15 hp boat motor into 25 hp boat motor?

To change a 15 hp boat motor into a 25 hp motor, you typically need to upgrade several key components, including the carburetor, exhaust, and possibly the ignition system, to allow for increased fuel and air intake. Additionally, you may need to modify or replace the engine's internals, such as the pistons and cylinder head, to handle the increased power output. However, it's important to note that such modifications can affect the motor's reliability and may void any warranties. Always consult with a professional or the manufacturer before making significant changes.