In looking at the specs for new Mercury motors, the engine displacement for the 2.5 and the 3.3hp is the same. The only difference is the gear ratio: the 2hp is 1:85:1, and the 3hp is 2:15:1 The 4hp and the 5hp are identical in displacement, and gear ratio. How can you get more power from the same size engine? Is there some simple trick I can do to pump up my little 2hp Yamaha without ruining it? I really like tinkering with engines but I don't want to mess it up. Thanks for your help.