PSS Bellows Replacement: The 6-Year Service
The PSS Type A has one major scheduled service item: the nitrile rubber bellows that carries the carbon flange and keeps the seal faces pressed together. Official PSS guidance is to replace it roughly every six years, and for most owners it's a yard job folded into a regular haul-out. This guide covers why the bellows is the part that ages, when to do the job, what goes in the box and how the replacement runs — from Luxfords Marine, the authorised Australian PSS distributor, serving boat owners since 1963.
Why the bellows is the service item
The Type A is a mechanical face seal. A 316L stainless rotor, sealed to the shaft by two o-rings, spins against a stationary carbon flange lapped flat to four helium light bands. Those two faces do all the sealing — and neither of them rides on the shaft. The component working quietly in the background is the PSS shaft seal bellows: a nitrile rubber bellows clamped over the stern tube, whose pre-load compression keeps the faces mated while it absorbs propeller thrust, misalignment and vibration.
Nitrile rubber sitting below the waterline ages the way any underwater rubber hose does, and PSS says to treat it the same way: inspect it as part of your routine checks, and replace it on schedule — official PSS guidance is roughly every six years. (The PSS PRO uses a reinforced silicone bellows rated for 8–10 years between replacements; we stock the Type A and can supply the PRO on request.)
When to do it
The bellows cannot be changed in the water — the shaft coupling has to come off — so the sensible time is a haul-out you were having anyway. Antifoul, anodes and the six-year bellows make a natural package, and many owners have the cutlass bearings checked or replaced on the same slipping. Our sister store, CutlassBearings.com.au (same family business), covers Exalto cutlass bearings Australia-wide.
What the 6-year service takes
The PSS Maintenance Kit
A new bellows, new o-rings, new set screws and new hose clamps — one box holding every consumable the service uses, matched to your seal size.
Fresh set screws, always
The cup-point set screws bite into the shaft the first time they're torqued. Once bitten they never go back in — always fit the new screws from the kit.
A scheduled haul-out
The coupling must be unbolted and the boat out of the water, so bundle the job with antifoul, anodes and cutlass bearings to save a lift.
Shaft seal bellows replacement, step by step
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1
Haul out
The bellows is serviced with the boat on the hard. Book the job into a scheduled slipping alongside antifoul and anodes rather than paying for a special lift.
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2
Uncouple the shaft coupling
The bellows is a closed ring of rubber with no split to open — it slides on and off over the end of the shaft. That means unbolting the shaft coupling before anything else.
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3
Back off the rotor
Loosen the two pairs of set screws, set at 90 degrees to each other, and slide the stainless rotor along the shaft. The old screws are finished — their cup points have already bitten into the shaft, and they are never reused.
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4
Remove the old assembly and clean the shaft
Slide the old bellows and carbon flange off over the shaft end, then clean the shaft with soapy water only. Never use petroleum grease or silicone anywhere near a PSS seal.
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5
Fit the new bellows and carbon flange
Slide the new bellows and carbon flange up the shaft and clamp them over the stern tube using the new hose clamps from the Maintenance Kit.
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6
Refit the rotor and set the pre-load
Fit the new o-rings, then compress the bellows to the official chart: 3/4" (20 mm) for shafts from 3/4" to 1-3/8", and 1" (25 mm) for shafts from 1-1/2" to 3-3/4". Torque the new set screws — about 6 ft-lb on small shafts, 8 ft-lb on large — then fit the locking screws on top (a second screw seats in each hole to lock the first).
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7
Reconnect, relaunch and burp the seal
Re-bolt the coupling and relaunch, then vent ("burp") the seal as part of the relaunch. The venting requirements for boats above and below 12 knots are detailed on our installation page.
A yard job for most owners
None of this is exotic, but it involves uncoupling the shaft, setting the pre-load compression accurately and re-bolting the coupling — which is why most owners hand the PSS six-year service to the yard while the boat is already out for antifoul. If you're tackling it yourself, the complete pre-load, torque and venting specification lives on our installation page, and the routine checks between services are covered in our maintenance guide.
To get the right PSS Maintenance Kit, call us on (03) 5973 6444 with your shaft diameter — or identify your seal first with the seal finder, which shows every PSS Type A that fits your shaft and stern tube, with live stock and prices in AUD including GST.
PSS bellows replacement FAQs
How often should the PSS bellows be replaced?
Official PSS guidance is to replace the Type A's nitrile bellows about every six years — the same discipline you'd apply to any underwater rubber hose. The PSS PRO's reinforced silicone bellows extends that interval to 8–10 years between replacements.
What's in the PSS Maintenance Kit?
A new bellows, new o-rings, new set screws and new hose clamps — every consumable the six-year service uses. A separate PSS O-Ring Kit (2 o-rings, 5 set screws, allen wrench, clamp jackets and thread-lock) covers o-ring jobs between bellows changes.
Can the bellows be replaced with the boat in the water?
No. The bellows is a closed ring that slides on over the end of the shaft, so the shaft coupling must be unbolted and the boat hauled out. Plan the job into a scheduled slipping alongside antifoul and anodes.
Do the set screws really need to be replaced?
Yes. Their cup points bite into the shaft the first time they're torqued down, and once bitten they can't be trusted to hold again. The Maintenance Kit includes fresh set screws — always fit the new ones.
Due for your 6-year service?
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