|Thanks one and all. I'll certainly be checking ebay for a replacement prop(another brand of folder, as I race). I believe the rattling/shaking is the Gori not fully opening, because if I go from reverse to forward with the boat still moving aft, the problem does not occur - presumably because this situation pushes the blades to open fully. As well, depending on sea state and monoeuvering, the shaking sometimes smooths out after a few minutes and I can go to high revs with no problem. Finally, I had the same problem with a Gori on my last boat and never could cure it!