Maxwell-nilsson horizontal windlass

[cabos]

I got a Maxwell-Nilsson windlass on board my hunter passage (1991). To lift the anchor, we usually tighten the clutch ring at the far right for the winch and operate the motor.
Recently, although the cluch is fully tighten, the gypsy slips backwards (it does turn but the weight of the anchor turns it backwards.) as if the clutch does not working properly. Any ideas??? anyone has a manual for this windlass?
thanks

 

[Saillife]

Have you seen this?
http://biankablog.blogspot.com/2009/07/repairing-maxwell-nilsson-vr-700.html