I did some research and learned where this 3.5 HP rating came from and it's not 3.5 HP. It is 3.5 Peak HP. That rating is obtained by putting the motor on a test bench and monitoring the current while a brake is applied to the motor. As the current increases due to the brake force the current is recorded. When the motor finally stalls the current is shown to be approximately 32 Amps.
Do the math:
115 Volt x 32 Amp x .72 (eff) / 746 = 3.5 Peak HP
I. E. it's a sales gimmick that doesn't tell you much except that each bench test toasts a motor.
I'm running 225 feet of extension cord. That's 200 feet of 12AWG and 25 feet of 14AWG. I also installed a fuse box in series with the cords. I started with a 5 Amp slo-blo. It held for approximately a minute then opened. Then I installed a 7 Amp slo-blo and have been cutting since then. I'm cutting out stumps so believe me this little Poulan ES350 is standing up to my test bench.
With my 225 feet of cord I'll guess that I'm getting:
110 Volt x 6 Amp x .72 (eff) / 746 = 0.6 HP
Even that 0.6 sounds like a lot for these little dinky motos. But who am I to argue with the numbers?