How can i test the power output of my Honda 2000i?

I agree with the others. There are two wattage ratings to every generator, surge and continuous, and the former is always higher than the latter. I think you'll find the 2,000 watt rating on the Hondas is for surge, and if I remember correctly, the continuous is 1800 watts. You are putting an 1875 watt continuous load on that generator, and I'd expect it to be taxed. I'm surprised it doesn't kick itself offline.