Off the bottle my engines turned 7800-8000rpm and performed great. On the bottle they turned 8600-8800rpm. Same props. It just added to the acceleration and top speed. These engines really came to life on the juice! Reliable too. Only failure in 5 seasons I had was a broken prop shaft when punching off around 50mph on the bottle. With no load on the engine it instantly wound-up to around 10,000rpm and took out the upper crank bearing.