I just bought a NFB (no-feedback) helm and cannot turn the shaft by hand. Why?

Without the steering wheel on the shaft, NFB helms are very difficult to turn by hand. The reason is that the no-feedback clutch is always on standby to grip the helm shaft and hold it steady against torque feedback from the engine (which can make the steering wheel turn on non-NFB systems). Once the helm is mounted in the dash and the steering wheel is properly attached, you will be able to turn the shaft with a little pressure on the wheel. Follow the installation instructions completely.