Unfortunately B&S quote gross power, David, which is considerably more than can be extracted from the engine as delivered to the customer without modifying it. Honda's "maximum" figure is similar to B&S's gross power. Gross power should not be described as either net or continuous, it is neither of those.
You can read some of the sad story here:
http://www.yourlawyer.com/topics/overview/Lawnmower_Horsepower_Fraud
