PSS Shaft Seal Maintenance
Here's the honest headline: a PSS Type A dripless shaft seal needs almost no routine maintenance. There's no packing to tighten, no repacking at haul-out, no steady drip to manage in the bilge. But almost none isn't none — the little a PSS seal does ask for is what keeps it dripless year after year, and most of it takes minutes.
Quick recap: a 316L stainless-steel rotor clamped to the propeller shaft spins against a stationary carbon flange on a nitrile rubber bellows clamped over the stern tube; bellows compression keeps the faces mated. The parts that age are the rubber ones — bellows and o-rings — so that's where the maintenance lives. New to the design? Start with how a PSS seal works.
The annual look-over
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1
Inspect the bellows
Treat the bellows like any other underwater rubber hose: inspect it regularly for cracks, perishing or soft spots — at every haul-out, and whenever you're in the engine bay anyway.
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2
Check the hose clamps
The bellows clamps over the stern tube with hose clamps. Confirm they're tight and in good condition.
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3
Make sure the faces stay wet
The carbon and stainless faces are water-lubricated. Check the vent hose or water feed is connected and clear, and burp the seal after any relaunch.
The six-year bellows rule
Official PSS guidance is to replace the bellows about every six years. The PSS Maintenance Kit turns that into one tidy job: it includes the new bellows plus new o-rings, set screws and hose clamps, so every ageing part of the seal is renewed at the same time. Our bellows replacement guide walks through the job step by step.
If the rotor comes off but the bellows stays — say the shaft has been pulled — the O-Ring Kit covers it: two o-rings, five set screws, an allen wrench, clamp jackets and thread-lock.
| Kit | What's included | When you need it |
|---|---|---|
| PSS Maintenance Kit | New bellows, o-rings, set screws and hose clamps | The roughly six-year bellows replacement |
| PSS O-Ring Kit | 2 o-rings, 5 set screws, allen wrench, clamp jackets, thread-lock | Rotor re-fits — e.g. after pulling the shaft |
PSS set screws: they only bite once
The rotor is held to the shaft by two pairs of set screws at 90 degrees. Each screw has a cup point that bites into the propeller shaft — and it only bites properly once. Never reuse a set screw on the shaft.
Any time the rotor is disturbed, fit fresh screws with thread-lock. The O-Ring Kit includes five, and the second screw in each pair — which locks the first without touching the shaft — can be swapped into the biting position. Snug them firmly with thread-lock — they lock the rotor at the position set during installation, when the bellows is compressed to its pre-load. Our installation guide covers getting that compression right.
Burping the seal, and keeping the water coming
Whenever the boat is relaunched, vent — burp — the seal so trapped air escapes and water reaches the faces. It takes a moment and keeps the seal from running dry.
How water reaches the seal depends on boat speed:
- Under 12 knots: the seal vents through a 3/8" hose run at least 2 ft (about 600 mm) above the waterline, with no loop in the run that could set up a siphon.
- Over 12 knots: the seal needs a positive water feed, at no more than 10 PSI.
- Twin engines: if the boat can exceed 12 knots on one engine, a crossover line between the two seals is required so both stay fed.
The don'ts
No oil or grease
Never use oil, grease or any petroleum product on the seal or bellows — not during assembly, not as a fix.
No silicone
Silicone is off the list too. The only assembly lubricant PSS allows is soapy water.
Never run dry
The faces need water. Burp the seal on relaunch and keep the vent hose or water feed clear.
Never reuse set screws
Cup points bite once. New screws and thread-lock at every refit — the O-Ring Kit includes five.
When maintenance becomes replacement
Two things call time on a seal rather than a kit: a scored rotor face, or a genuinely tired bellows on a seal that owes you nothing. At that point it's a measuring job, not an engine question — PSS fits any standard shaft installation from 3/4" to 3-3/4" (20–95 mm), sized by propeller shaft diameter and stern-tube outside diameter, whatever badge is on the engine.
Measure both and the seal finder lists every seal for your shaft with the stern-tube range each one covers, live Australian stock and AUD prices including GST. In-stock sizes dispatch fast Australia-wide; the rest are special order, dispatched in 2–3 weeks. The smart time to do it all is the haul-out you've already booked — antifoul, anodes, bellows, and while the shaft is accessible, the cutlass bearings; our sister store CutlassBearings.com.au carries Exalto bearings for the same job.
PSS shaft seal maintenance FAQs
What maintenance does a PSS dripless shaft seal need?
Very little. Inspect the bellows regularly like any underwater rubber hose, check the hose clamps, make sure water is reaching the faces, and replace the bellows about every six years with the PSS Maintenance Kit. There's no packing to tighten and nothing to grease.
How often should the PSS bellows be replaced?
About every six years, per official PSS guidance. The PSS Maintenance Kit includes the new bellows plus new o-rings, set screws and hose clamps, so every ageing part is renewed in one job.
Can I reuse PSS set screws?
No. Each set screw has a cup point that bites into the propeller shaft once, and a reused screw can't grip properly. Fit new set screws with thread-lock at every refit — the O-Ring Kit includes five.
What is burping a shaft seal?
Burping — venting — the seal means letting trapped air escape after relaunch so water reaches the carbon and stainless faces. Do it every time the boat goes back in the water; the faces are water-lubricated and should never run dry.
Can I use grease or silicone on a PSS shaft seal?
No. Never use oil, grease or any petroleum product on the seal, and never use silicone. The only assembly lubricant PSS allows is soapy water.
Kits, set screws or a new seal — sorted from Mornington
Mon–Fri 8:00am–4:30pm · sales@luxfords.com.au · Authorised Australian PSS distributor — Luxfords Marine, supplying quality marine products since 1963.