Prop is spinning freely


Chris Likins
 

We have A54 #133. Today when sailing I noticed that the prop was spinning freely(in reverse) each time a wave would pass under us. It’s easy to see that the shaft brake is not engaging when the engine is in neutral or shut down. Referencing Bill Rouses book p.305, it reads that the hydraulic shaft OPENS the calipers when pressurized by the transmission. Currently the shaft is retracted into the piston at all times allowing the calipers to remain open. I understand that the calipers are supposed to spring shut on the disk when transmission pressure is lost on the shaft. I am a bit confused by this as there is no mechanical connection between the hydraulic shaft and the outer caliper. It seems like the calipers should close when the shaft is extended.. So my questions are
1. Can someone help explain this system in more detail? 
2. What position should the shaft be in when pressurized and not pressurized? 
3. Is it most likely a bad spring on the caliper? 
4. Most importantly for now.. Is it ok to allow the prop to spin freely for the duration of the passage or would it be better on the shaft if we remain in forward gear. 

Thank you for the help! 

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