Further to oil filled stern tubes, the boat I was talking about has been in the water for about 10 years now with zero maintenance.
Pit corrosion can be a problem in any shaft, I had it in a shaft inside the stuffing box on a boat 25 years ago - strangely there was no leak and it rarely needed to be tightened. The shaft was 35 years old when I replaced it due to wear. Stainless needs a molecular coating of oxide to be corrosion free and so anywhere there is oxygen starvation there can be a problem hence the rust streaks from behind some chain plates.
The largest trawler in town here has a similar set up except the shaft bearings are white metal and the stern tube is full of grease. Gets replaced every 10 years or so. Couple of pumps on the permanently connected grease gun every now and again.
Select to expand quoteRamona said..
The largest trawler in town here has a similar set up except the shaft bearings are white metal and the stern tube is full of grease. Gets replaced every 10 years or so. Couple of pumps on the permanently connected grease gun every now and again.
shed be a ripper 
Someone on the forum a long time ago suggested to treat your PSS as a consumable and
just change it every ten years. Seems about right to me.
The manufacturer recommends changing the rubber bellows at 6 years maximum.
Limk to the manual belowhttp://www.pyiinc.com/images/pdf/pss/PSS%20installation%20instructions%20(low%20res).pdf
The manual also notes that sqealing can be a result of lack of water, so it may be worthwhile checking the bleed line, though I could not see the bleed line in the photos? A squeal may be different to a whine, probably depends on the mood the parent is in!
My PSS seal squealed for about 10'hours or so of running after every anti foul. I never worked out why, though "burping" by pulling the seal open to let water through seemed to help. I changed the seal last anti foul and that helped.
Thanks for all the advice guys.
The previous owner has fit a dry seal - there is no provision on the bellows to fit a water injection point.
I am reluctant to lift the boat out of the water until November when we return from having lots of fun around the Whitsundays and places in between.
When it is lifted out, it will be anti fouled, prop speed, shaft seal and a few other minor jobs.
So in the meantime, I will keep the revs down around 1500 - 1600 where it doesn't whine or squeal, and I will closely monitor it.
If all else fails, I have 3 good bilge pumps!
Thanks again for the helpful advice.
One other thing to check is the end float in prop shaft and engine mount flex( if you have flexible mounts)
Is the shaft locked into the coupling and not just floating on a keyway?,,gradually creeping back and forth according to which gear you have selected.
A reference mark on the shaft with a chemi pen and a mark on the hull will indicate whether the shaft is moving forward under higher rpm/thrust.
Forward movement of the shaft will reduce the preload of the seal.
Whilst it would take a lot of endfloat to unseat the seal face and is highly unlikely, a small amount of endfoat may disturb a seal that has the incorrect preload measurement inplace.
