Torque is not a power measurement and to be honest, I hate Briggs and Stratton using it on their engines. I understand why they went to it, but I don't agree with it.
You're right, if the Predator engine can burp out 8.1 ftlbs @ 4250 rpm in stock form then it'll do 6.5 HP.
I don't care how they rate an engine's power as long as they use a unit of power and follow a standard.
It can be Watts, Horsepower,Volt Amps, I don't care. But torque alone isn't one of them. Torque alone as it is on the advertisements is completely useless.
K, I'll stop complaining on the thread.
Power is useless when it is not rated at the RPM the motor is being run at. If there was some standard for these motors that said HP is rated at 3600 rpm then fine. Until then I prefer the TQ number since it will be fairly close to the peak number in the 3000 rpm range... After that I can do the math if I want the HP number...