Over the winter, our PSS seal began leaking between the collar (affixed to the shaft) and the bearing attached to the bellows - in other words, right where it is supposed to seal! It turns out that the collar had migrated forward on the shaft from the constant pressure of the bellows. The boat is 10 years old with about 2000 hours on the engine. The stainless steel set screws were all in place, but they had worked a groove along the softer bronze shaft as the collar worked its way forward. At haulout this past week, I was able to get a good look at it. The collar had worked forward about three-quarters of an inch, about the amount the bellows were compressed when installed. The grooves from the set screws were obvious. I removed the grub screws, cleaned up the shaft with emery paper and slid the collar back to where it belonged, compressing the bellows again. I installed the inner and outer grub screws with lots of loctite. Happily, the o-rings still sealed around the shaft, and all was well again on relaunch. To keep it from moving forward again, I clamped a zinc around the shaft against the collar. There may be a neater clamp or some such that would do the same job. To those with PSS seals on bronze shafts, it might be worthwhile to check the amount of pressure your bellows are exerting to ensure you don't have the same problem. It would also be an idea to place a band of tape or some mark on the shaft ahead of the collar so that if the collar moves, it will be apparent.