PSS vs Tides Marine SureSeal
These are two different sealing technologies, not two versions of the same thing. The Tides Marine SureSeal is a lip seal that runs directly on your propeller shaft, carries a spare seal you can change in the water, and needs a water feed line on every installation. The PSS is a mechanical face seal that seals at its own lapped carbon and stainless faces instead of against the shaft surface, which is why it suits worn shafts and only needs a plumbed water feed above about 12 knots.
PSS and Tides Marine side by side
Published manufacturer figures only. Where a maker does not publish a figure, the table says so rather than guessing.
Seal type
PSS Shaft Seal
Mechanical face seal - a stationary carbon stator running against a rotating 316L stainless rotor, loaded by a compressed bellow
Tides Marine
Lip seal - a nitrile/aramid lip with a 316 stainless garter spring riding directly on the shaft, inside a housing with an integral PTFE bearing
What actually seals
PSS Shaft Seal
The lapped faces. The rotor's O-rings sit statically on the shaft and turn with it, so the shaft surface is not a wear surface
Tides Marine
The shaft surface itself. Tides' own troubleshooting guidance covers polishing the shaft and sliding the unit to a fresh section of shaft
Shaft size range
PSS Shaft Seal
Type A: 3/4" to 3-3/4" (20-95 mm). Type B and C continue to 8" (203 mm) on special order
Tides Marine
SureSeal catalogue charts: 7/8" to 8", and 25 mm to 150 mm
Tides' homepage summarises the range as 1-8 inch / 25-160 mm while its catalogue charts start at 7/8 inch and stop at 150 mm. The catalogue figures are used here.
Water feed
PSS Shaft Seal
Required above about 12 knots, and for displacement boats with a bearing in the shaft log, boats whose stern tube can leave the water, and twins that exceed 12 knots on one engine. Slower boats run a vent line instead
Tides Marine
Required on every installation at all speeds - roughly 4 L/min at idle and a minimum 2 psi, with a crossover line on twins so a shut-down engine's seal still gets water
Setting up at install
PSS Shaft Seal
The bellow is compressed to a published figure for the size - measured at fitting
Tides Marine
The convoluted articulating hose self-sets the operating distance: "No measurements are required"
Spare seal on board
PSS Shaft Seal
No in-service spare. A maintenance kit is carried as a spare part
Tides Marine
The Spare Seal Carrier holds one or two spare lip seals on the shaft so a worn seal can be changed in the water without uncoupling the shaft
The carrier is ordered separately - it is not in the standard SureSeal kit - and fitting one needs at least 1.25 inches more shaft length.
Scheduled replacement
PSS Shaft Seal
Bellow every 6 years regardless of apparent condition, inspection at least 6-monthly. Replacement is a haul-out job
Tides Marine
No service life or lip seal replacement interval is published. Maintenance is condition-based - replace the lip seal when it leaks
Spare parts
PSS Shaft Seal
Maintenance kit published and itemised: bellow, set screws, O-rings, 316L clamps, clamp jackets, thread lock, wrench and instructions
Tides Marine
Replacement lip seals and spare seal carriers published as separate parts. Tides' 48-hour replacement-parts commitment is written for US customers
Certification
PSS Shaft Seal
Manufacturer states Bureau Veritas, ABS and RINA certification; no certificate numbers or scope published
Tides Marine
ABS type approval, a Lloyd's Register certificate and ISO 9001:2015 (NQA cert 11148-11889), published as documents
Warranty
PSS Shaft Seal
3 years from first use or shipment, original purchaser only
Tides Marine
2 years or 2,500 engine hours, whichever comes first. No warranty on engines of fewer than four cylinders; governed by US maritime law with warranty assistance available through the UK, Spain and Australian offices
Australian support
PSS Shaft Seal
Luxfords is an authorised PSS dealer holding one of Australia's largest ranges in stock.
Tides Marine
Tides Marine Australia (Noosaville, QLD) is the manufacturer-listed Asia-Pacific agent, and several Australian marine businesses resell the SureSeal
| Specification | PSS Shaft Seal | Tides Marine |
|---|---|---|
| Seal type | Mechanical face seal - a stationary carbon stator running against a rotating 316L stainless rotor, loaded by a compressed bellow | Lip seal - a nitrile/aramid lip with a 316 stainless garter spring riding directly on the shaft, inside a housing with an integral PTFE bearing |
| What actually seals | The lapped faces. The rotor's O-rings sit statically on the shaft and turn with it, so the shaft surface is not a wear surface | The shaft surface itself. Tides' own troubleshooting guidance covers polishing the shaft and sliding the unit to a fresh section of shaft |
| Shaft size range | Type A: 3/4" to 3-3/4" (20-95 mm). Type B and C continue to 8" (203 mm) on special order | SureSeal catalogue charts: 7/8" to 8", and 25 mm to 150 mm |
| Tides' homepage summarises the range as 1-8 inch / 25-160 mm while its catalogue charts start at 7/8 inch and stop at 150 mm. The catalogue figures are used here. | ||
| Water feed | Required above about 12 knots, and for displacement boats with a bearing in the shaft log, boats whose stern tube can leave the water, and twins that exceed 12 knots on one engine. Slower boats run a vent line instead | Required on every installation at all speeds - roughly 4 L/min at idle and a minimum 2 psi, with a crossover line on twins so a shut-down engine's seal still gets water |
| Setting up at install | The bellow is compressed to a published figure for the size - measured at fitting | The convoluted articulating hose self-sets the operating distance: "No measurements are required" |
| Spare seal on board | No in-service spare. A maintenance kit is carried as a spare part | The Spare Seal Carrier holds one or two spare lip seals on the shaft so a worn seal can be changed in the water without uncoupling the shaft |
| The carrier is ordered separately - it is not in the standard SureSeal kit - and fitting one needs at least 1.25 inches more shaft length. | ||
| Scheduled replacement | Bellow every 6 years regardless of apparent condition, inspection at least 6-monthly. Replacement is a haul-out job | No service life or lip seal replacement interval is published. Maintenance is condition-based - replace the lip seal when it leaks |
| Spare parts | Maintenance kit published and itemised: bellow, set screws, O-rings, 316L clamps, clamp jackets, thread lock, wrench and instructions | Replacement lip seals and spare seal carriers published as separate parts. Tides' 48-hour replacement-parts commitment is written for US customers |
| Certification | Manufacturer states Bureau Veritas, ABS and RINA certification; no certificate numbers or scope published | ABS type approval, a Lloyd's Register certificate and ISO 9001:2015 (NQA cert 11148-11889), published as documents |
| Warranty | 3 years from first use or shipment, original purchaser only | 2 years or 2,500 engine hours, whichever comes first. No warranty on engines of fewer than four cylinders; governed by US maritime law with warranty assistance available through the UK, Spain and Australian offices |
| Australian support | Luxfords is an authorised PSS dealer holding one of Australia's largest ranges in stock. | Tides Marine Australia (Noosaville, QLD) is the manufacturer-listed Asia-Pacific agent, and several Australian marine businesses resell the SureSeal |
Figures from the Tides Marine SureSeal catalogue, Tides' published warranty policy and distributor listings, and the PSS Shaft Seal catalogue and Type A installation instructions, checked August 2026. Where a maker does not publish a figure, this table says so rather than estimating.
When Tides Marine makes sense
- You want to change a seal without hauling out. The Spare Seal Carrier is the SureSeal's headline advantage and it is a genuine one - a worn lip seal can be swapped afloat, without uncoupling the shaft from the gearbox.
- Your shaft is new or in excellent condition. A lip seal wants a smooth, unpitted shaft to run on, and on a clean shaft it does that job well.
- You want published class documentation. Tides publishes its ABS type approval, Lloyd's Register certificate and ISO 9001:2015 certificate as downloadable documents.
- The boat came with one and it is working. If a SureSeal is installed, plumbed and behaving, there is no engineering reason to change technology - buy the lip seal and carry a spare.
- You are replacing like for like on a boat over 3-3/4 inch shaft where our stocked PSS Type A range stops and a special order does not suit your timing.
When PSS is the better choice
- Your shaft is worn, scored or lightly pitted. A face seal seals at its own lapped faces, so the shaft's surface condition is not what holds the water back - this is the single biggest practical reason boats change over.
- You want the water feed to be optional rather than universal. Under about 12 knots a PSS runs on a simple vent line, where the SureSeal requires a plumbed feed on every installation.
- You want a published maintenance clock. PSS publishes a hard 6-year bellow interval and an itemised kit, so the job can be budgeted and scheduled rather than waiting for a leak to tell you.
- The seal may see brief dry running. The PSS carbon is rated to 500F (260C) and the manufacturer states it will not melt during a short dry run, where a rubber lip is the part at risk.
- You want parts on a shelf in Victoria. Luxfords is an authorised PSS dealer holding one of Australia's largest ranges in stock. Most shaft and stern tube combinations ship the same day, and maintenance kits, spare bellows and carbons are stocked here rather than ordered from overseas.
Why the sealing surface matters
Both the Tides Marinesystem and the PSS keep the bilge dry. The difference is where the wear happens. A lip seal presses a flexible lip against the spinning shaft, so the shaft's own surface is part of the seal - which is why lip seal guidance talks about polishing the shaft or moving to a fresh section of it.
The PSS moves that job off the shaft entirely. A stationary carbon stator runs against a rotating 316L stainless rotor, and the rotor's O-rings sit statically on the shaft and turn with it. Nothing rubs the shaft, so a shaft already scored by old packing or a previous seal is usually still fine to seal on, and the carbon - rated to 500F - survives the brief dry run that would finish a rubber lip.
It is not a free lunch. The bellow is a consumable on a published six-year clock and replacing it means a haul-out, and above about 12 knots the seal needs a plumbed water feed. Those are the trade-offs, and they are on the table above.
PSS vs Tides Marine: common questions
Can I replace a Tides Marine seal with a PSS seal?
Usually yes, and it is a common conversion. Both clamp to the same stern tube, so the boat is hauled, the coupling comes off and the shaft normally stays in the boat. The two things to check first are the length of stern tube you have exposed and your shaft diameter and stern tube OD, because the PSS is sized on both. Send us those three measurements and we will confirm the exact part before you commit to the haul-out.
Does the PSS need a water line like the SureSeal does?
Not always, and that is a real difference. Tides requires a water feed on every SureSeal at all speeds. PSS requires a plumbed feed above about 12 knots, and in three other published cases: displacement boats with a bearing in the shaft log, boats whose stern tube can come out of the water, and twin-engine boats that can exceed 12 knots on one engine. Below that, a PSS runs on a vent line to at least two feet above the waterline.
Which one is better if my shaft is worn?
The PSS, clearly. A lip seal seals against the shaft surface, so pitting or scoring under the lip is what ends its life - Tides' own guidance is to polish the shaft or move the unit to a fresh section. A PSS seals at its own carbon and stainless faces, with static O-rings on the shaft, so a shaft that has been scored by old packing or a previous lip seal is usually still fine to seal on.
Can I change a PSS seal in the water like a Tides lip seal?
No, and we would rather say so plainly. The SureSeal's spare seal carrier is designed for exactly that and it is the strongest argument for the Tides system. The PSS trade-off is that its scheduled work is rarer and predictable - a bellow every six years at a haul-out, rather than a seal change whenever the lip lets go.
How long does each one last?
PSS publishes a preventive interval: replace the bellow no less than every six years regardless of condition, with six-monthly inspections, and the manufacturer states the carbon and rotor should not normally need replacing. Tides publishes no service life or replacement interval for its lip seals at all - maintenance is condition-based, which is why the spare carrier exists. Neither approach is wrong; they are different maintenance philosophies.
Is Tides Marine supported in Australia?
Yes. Tides Marine Australia in Noosaville, Queensland is the agent listed by the US manufacturer for the Asia-Pacific, several Australian marine businesses resell the SureSeal, and Tides' warranty document says warranty assistance can be handled through its Australian office. We would not suggest otherwise. What we offer is PSS parts on our own shelf in Mornington and someone who will talk through the sizing with you.
Changing over from Tides Marine?
Send us your shaft diameter, stern tube OD and how much stern tube you have exposed - that is all we need to confirm the exact PSS part and quote it, usually from stock.
Luxfords is an authorised PSS dealer holding one of Australia's largest ranges in stock — most shaft and stern tube combinations are on the shelf, so we can usually have you sorted straight away.
(03) 5973 6444Get a PSS seal quote
Tides Marine is a trademark of its respective owner and is used here only to identify the product being compared. Luxfords is not affiliated with, endorsed by or sponsored by Tides Marine.