[rgp]

From the max prop manual

If your propeller has been greased properly it will feather in a fraction of a second as soon as
you stop the shaft from freewheeling. DO NOT kill the engine while in reverse. In this case the
blades will be in the reverse position and cannot feather. You can actually use this feature to drive
a shaft alternator.
Modern transmissions are either mechanical or hydraulic. With a mechanical transmission, the
best way to stop the shaft freewheeling is to engage the transmission in reverse (WARNING:
engage the reverse only after the engine has stopped completely). With a hydraulic transmission
you must shut off the engine while still engaged in forward. The remaining hydraulic pressure will
en effect lock the shaft for a few moments, enough for the MAX PROP® to feather.