I have an older Yamaha 9.9 hp 2 cycle outboard that I use on an Avon inflatable. Had it rebuilt 2 years ago but it just doesn't seem to have enough hp to move around with the the number of people that are usually at the boat. <br /><br />So I was wondering. There doesn't seem to be much difference between the 9.9 and 15 hp models. Is there some way I can upgrade the 9.9 to 15 hp? <br /><br />Joeyd
