Need some "special" horsepower

Heya, long time poster on the endless-sphere forum, and I have a question for you guys. I am looking at building a generator trailer for my E moto. There are some things gas motors are still pretty dang good at. I am familiar with the electrical side of things so once I get a spinning shaft, I got it from there. BUT I need a motor, the performance goals I am after are these:

Weight: sub 30lbs for the motor
Horsepower: need about 5hp of output. Real output. Like 3-4 hours at a time output.
As quiet as possible, but I suppose its not necessary.
RPM: anything between 2k and 8k faster is better.
Cost: 300 bucks sound doable?

Here is some dyno pr0n for you guys. 24hp and 154ft/lb at the wheel. First place at bairdco riverside race in sept.


m.youtube.com/watch?v=bwoGXQDzB-s

Thanks man, I like that HF engine, and rated at 7hp it can probably be idled down a small amount and add a little lifespan and quietness. Or is that 7hp downhill with a tailwind in perfect factory conditions? What kind of horses do those powerbees make? A quick search shows powered parachute guys making almost 20 hp out of them . They seem to be a pretty lightweight looking engine. But they are a lil spendy.