How a PSS dripless seal works — and how to measure for yours
A PSS Type A seal replaces your stuffing box with a completely dripless mechanical face seal. To find the one that fits, we need just two measurements: your propeller shaft diameter and your stern-tube outside diameter. Enter both and our finder returns every seal that fits.
Not sure what you’re looking at? We’ll confirm the fit over the phone — (03) 5973 6444.
How a PSS seal works
The PSS Type A is a mechanical face seal. A polished stainless rotor clamps to your propeller shaft and spins with it, pressed against a stationary carbon flange. A nitrile rubber bellows fits over your stern tube and holds those two faces together. The bellows pre-load keeps the seal closed while absorbing propeller thrust, shaft misalignment and vibration — so there are no drips, no packing and far less maintenance than a traditional stuffing box.
Stainless rotor
A 316L stainless rotor (Nitronic 50 optional) clamps to your shaft and spins with it — the rotating half of the seal.
Carbon flange
A resin-impregnated carbon stator, lapped flat to 4 helium light bands, stays still. The rotor runs against it to make the dripless seal.
Nitrile bellows
A moulded nitrile bellows slips over the stern tube and is held with hose clamps. Its pre-load keeps the two faces together.
Water lubrication
A hose-barb vent feeds water to the faces, lubricating and cooling them. Rated to 10 PSI, −15°C to 107°C and up to 10,000 RPM.
Why go dripless
A traditional packing gland is designed to drip — it relies on a steady weep of water through the packing to stay cool, which means constant water in the bilge and regular adjustment. A PSS seal does away with all of that.
No drips in the bilge
The face seal is completely dripless. No constant weep means a drier bilge and a bilge pump that runs far less often.
Less maintenance
No packing to repack and no gland to keep adjusting. Just inspect the bellows regularly and replace it about every six years.
Tolerant by design
The bellows pre-load takes up propeller thrust, shaft misalignment and vibration while keeping the seal firmly closed.
Genuine PSS parts
Authentic PSS components from your authorised Australian distributor — supplying quality marine products since 1963.
How to measure
A PSS seal is sized by two measurements. Take both, enter them in our finder, and we’ll list every seal that fits your boat.
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1
Measure the shaft diameter
Measure across your bare propeller shaft with calipers or a tape, at a clean, unworn section. Metric or imperial is fine — PSS fits shafts from 3/4″ to 3-3/4″ (20 mm to 95 mm).
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2
Measure the stern-tube OD
Measure the outside diameter of your stern tube (shaft log) — the fixed tube the shaft passes through — where the bellows will clamp over it. This is quoted in inches; we show millimetres alongside.
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3
Enter both in the finder
Pop both figures into our seal finder. We list every seal that fits your shaft and show the stern-tube OD range each one covers — then you pick the size that matches your tube.
Why a range, not a single number
The bellows flexes to seal across a small band — roughly a few millimetresabout 1/8″ of stern-tube OD per size. That’s why each seal shows an OD range: as long as your tube falls inside the band for a given size, that seal will fit. Measure twice — if your figure sits right on the edge of two ranges, give us a call and we’ll confirm the right one.
Not sure of your measurements?
With 60+ years supplying marine products, we’re happy to talk it through. Tell us your shaft and stern-tube figures and we’ll confirm the exact PSS seal before you order — or measure with confidence and use the finder now.