Well you are about twenty times over my perferred engine size but here is what I have seen in the slippin' prop department:

1. The shaft is not threaded far enough to allow the prop nut to tighten down on the prop. Or, the threads are bad at some point on the shaft. Solution - use a thicker prop washer or a thicker prop.

2. One, or more, of the players is too smooth; either the prop, washer, or thrust washer. Solution - Either change them or put a surface on that will grip. I had a problem with some fiberglass composite props slipping and solved it by making some sandpaper "washers" that I CA'ed to the prop back.

3. The prop is compressing. Usually only a problem with soft wooden props and not likely with an APC. Solution - Chg the prop.

4. The prop nut is sloppy fit on the shaft because or worn, mis-matched, or buggered threads. Solution - Change the nut and hope the problem is with the nut and not the shaft.


CA might work and you can probably use nitro or debonder to remove it. I would also consider the 'wicking' LocTite (maybe it is #239 ?)if I was going that route.