Rebuilt Supercharger and High Idle?

[NoKENtrol]

I rebuilt the supercharger in my 2006 Sportster - upgraded to a Riva Gen II impeller. After installing the SC, I pushed the boat outside, hooked up the garden hose, started the engine, and started the water. The engine fired up immediately and runs smooth. My only concern is that it is idling at 2400 RPMs. Is that too high? I wasn't sure if it made a difference on the RPMs from idling in water compared to idling on the trailer with the garden hose hooked up to it. Do you think I have a bad throttle position sensor? At 2400 RPMs, I think I will be scooting pretty fast in neutral when I am navigating in a no-wake zone. Thanks in advance for your advice/help/input.