Buying Guide

PSS Type A vs PSS PRO: Which Shaft Seal Do You Need?

Short answer: the PSS Type A and PSS PRO share the same proven mechanical face-seal design — a stainless steel rotor spinning against a lapped carbon flange, held together by bellows pre-load. The PRO upgrades the materials for demanding service: a reinforced silicone bellows with an 8–10 year replacement interval (versus about 6 years for the Type A's nitrile bellows), a secondary shaft retention collar, 316 stainless rolled-edge non-perforated hose clamps, and the Nitronic 50 rotor as an upgrade option (also available on the Type A on request). For most Australian recreational boats, the Type A is the right seal.

Both seals are made by PYI Inc (USA), the manufacturer of the PSS brand, and both are completely dripless. In each, the sealing surfaces sit off the shaft — the carbon flange, lapped flat to 4 helium light bands, runs against the stainless rotor, so the shaft itself is never a wearing part. If you want the full mechanical story, see how a PSS seal works. This page answers the practical question: which of the two belongs on your boat?

Side-by-Side Comparison

Which One Do You Need?

For most Australian recreational boats — cruising yachts, motor cruisers, weekenders — the Type A is the right seal. It is one of the most widely fitted dripless seals worldwide, it covers every shaft from 3/4" to 3-3/4" (20–95 mm), and its nitrile bellows is a known quantity: inspect it as you would any underwater hose and replace it roughly every six years with a PSS Maintenance Kit. Because we stock the range, an in-stock size dispatches fast anywhere in Australia.

The PRO earns its premium when the job is harder. PYI positions it for demanding, harsh, corrosive or high-pressure applications — hard-worked boats, aggressive environments, or installations where stretching the bellows interval to 8–10 years genuinely matters. The silicone bellows, retention collar and upgraded clamps are the same face seal in tougher materials, not a different sealing concept. If your boat lives an easy recreational life, those upgrades are nice to have; if it works for a living or runs in punishing conditions, they are worth pricing up.

Availability in Australia

We stock the PSS Type A range. Every size combination — shaft diameter by stern-tube OD — is listed in our seal finder with live stock and pricing in Australian dollars, GST included. Type A prices run from $872 to $5,421 depending on size; in-stock seals dispatch fast, and other sizes are special order, typically 2–3 weeks. Not sure of your measurements? Our sizing guide shows exactly what to measure.

The PSS PRO is available on request. It does not appear in the finder and is not a shelf item, but as the authorised Australian PSS distributor we can quote and supply any PRO size in the same 3/4" to 3-3/4" (20–95 mm) range. Call (03) 5973 6444 or email sales@luxfords.com.au with your shaft diameter and stern-tube outside diameter and we will come back with a price and lead time. And if you are still weighing PSS against lip-seal alternatives, our brand comparison covers the wider field.

PSS Type A vs PSS PRO: Your Questions Answered

What is the difference between the PSS Type A and the PSS PRO?

Both use the same mechanical face-seal design: a stainless steel rotor running against a lapped carbon flange, held in contact by bellows pre-load. The PRO upgrades the hardware for demanding service — a reinforced silicone bellows with an 8–10 year replacement interval instead of the Type A's roughly 6-year nitrile bellows, a secondary shaft retention collar, 316 stainless rolled-edge non-perforated hose clamps, and a Nitronic 50 rotor upgrade option.

Is the PSS PRO worth the upgrade?

It depends on how your boat works. For most recreational cruising yachts and motor boats the Type A is the right seal, and it is the version we keep in stock. PYI positions the PRO for demanding, harsh, corrosive or high-pressure applications, and that is where its longer-life silicone bellows, retention collar and upgraded clamps earn their premium. If your boat works hard or runs in punishing conditions, ask us for a PRO quote.

Are PSS Type A and PSS PRO sizes the same?

Yes. Both seals cover shaft diameters from 3/4 inch to 3-3/4 inches (20–95 mm), and both are selected using the same two measurements: shaft diameter and stern-tube outside diameter. Measure both and we can quote either seal for your boat.

Can I buy the PSS PRO in Australia?

Yes — on request. Luxfords Marine is the authorised Australian PSS distributor. We stock the Type A range, and we can quote and supply the PSS PRO in any size on request: call (03) 5973 6444 or email sales@luxfords.com.au with your shaft diameter and stern-tube outside diameter.