For an inland lake, it's overkill, you can't move the boat faster than the theoretical hull speed. However, if you already have one and your motor bracket is well backed on the inside of the hull, the bracket block is in good shape and the bracket is rated to support the weight and the thrust, then why not?
I have a 4hp and it is fine for my purposes, a large inland reservoir, but I see a lot of 6 to 9.9hp motors on boats of our size here.