I figured there would be a lot of different opinions on this topic. Sorry for rambling, but in short, I think you will be dissapointed with the performance of a new 9.9. I second the Tohatsu recommendation, since they make the 9.8 motors for mecury, and the tohatsu name is much cheaper. For comparison, a 2007 johnson 9.9 has a displacement of 18.4 cubic inches, where as a brand new mercury 9.8(made by Tohatsu) has a displacement of 12.8 cubic inches. If hp restriction is an issue, you are better off going with a used older 9.9, say in the 2000-2007 range. I dont know when or why they decided to choke down the 9.9 so much, but they did. As you can see, the 15hp is much more motor than the 9.9. If your talking cubic inches, the 9.9 is around 12.9 where the 15hp is around 21 or so. Whats the difference between the new 9.9 and 15 you ask? Well, the new 9.9 is about 209cc, and the 15 is around 351cc. If your going to buy new, spend the extra few hundred and get the 15hp. The new 9.9's are the same thing as a new 8hp, only difference is the carb.

15hp mercury motor