I have a 14ft Aluminum springbok that I bought last year. The 8 hp Evinrude that came with it works great but is not enough to get up on plane especially with another person in the boat. The plate says that the boat can handle up 20hp but I don't think the boat would even be touching the water with that kind of power. would a 9.9 be sufficient Or should I go with a 15? The boat has a fairly narrow body and not very deep. I don't want to buy something too big. The 8 gets me where I want to go but the boat is pushing alot of water and I am afraid I may be working the motor too hard. There are normally 2 of us in the boat all the time. Any suggestions?