Shaft Seal - PSS or Tides Marine Lip Seal ?

[Mark Johnson]

Greetings Extemp,
My information about the PSS recomendations is several years old. Perhaps yours is more recent? In my case, I have 6' of exposed shaft between the prop & the shaft log, so there is a cutlass bearing in the shaft log, where it exits the hull, as well as in the strut. This has minimal water flow and I wouldn't want little bits of growth & debris that is trapped in there to get into the PSS interface. This is why I prefer the water flow version on mine.

If the exit of your stern tube is wide open, and the shaft log short, (<18"), you don't have my problem and the "vent hose only" option seems reasonable. It also eliminates the slight extra risk of yet another fitting on your engine... Mark

[AnchorageGuy]

The need for the flow version of the PSS has more to do with boat speed than the length of the shaft or configuration. The vent method is recommended for boats that travel under 12 knots, in displacement hulls, to overcome forgetting to burp the bellows. This same installation will work quite well without the vent. Chuck

[Extemporaneous]

Ya, I can appreciate your need for the water supply because of restriction.
Cheers,
Extemp.

Originally Posted by Mark Johnson

Greetings Extemp,
My information about the PSS recomendations is several years old. Perhaps yours is more recent? In my case, I have 6' of exposed shaft between the prop & the shaft log, so there is a cutlass bearing in the shaft log, where it exits the hull, as well as in the strut. This has minimal water flow and I wouldn't want little bits of growth & debris that is trapped in there to get into the PSS interface. This is why I prefer the water flow version on mine.

If the exit of your stern tube is wide open, and the shaft log short, (<18"), you don't have my problem and the "vent hose only" option seems reasonable. It also eliminates the slight extra risk of yet another fitting on your engine... Mark

[cfarrar]

Our boat came with the non-vented PYI shaft seal. However, motoring into steep seas on one occasion caused the ingestion of air bubbles, the seal overheated, and the graphite disintegrated. We switched to the vented model.

[Extemporaneous]

Originally Posted by cfarrar

Our boat came with the non-vented PYI shaft seal. However, motoring into steep seas on one occasion caused the ingestion of air bubbles, the seal overheated, and the graphite disintegrated. We switched to the vented model.

Interesting.
Vented but not plumbed to a water supply, correct?

Thanks,
Extemp.

[delmarrey]

Originally Posted by Waterwayguy

The need for the flow version of the PSS has more to do with boat speed than the length of the shaft or configuration. The vent method is recommended for boats that travel under 12 knots, in displacement hulls, to overcome forgetting to burp the bellows. This same installation will work quite well without the vent. Chuck

To get this straight,
it is not just the boat speed (bubbles) but the RPM's of the prop shaft that need the water injection line to prevent over heating/extraction of air bubbles.

All PSS seals come with injections fittings now. Sail boats only need them as a burp line to keep the air out, UNLESS they have a small clearance between the shaft and tube, as described in my post above and that's why mine is pressurized.

[osirissail]

I would say that the speed of the boat is a function of the rpm's of the prop shaft. The higher the RPM's of the shaft the more heat is generated at the seal interface. As "cfarrar" said lack of cooling water can be a problem. So the vented version seems to be the only version now sold. Whether you use the vent as a vent or as a positive water injection system would be dependent upon RPM generated heat.

[pezquera]

Duncan:

You are only parked if you are in a car, in a sailingor cruising vessel you are either docked or anchored.

[Cranston]

I have a Tides shaft seal and it is quite reliable. One excellent feature is the spare seal carrier. If/when a seal goes, you can remove the old seal and slide a fresh one in place in a matter of minutes while in the water. Also, seals are off the shelf items so you don't need to buy direct from Tides - I found replacement seals in Guaymas at the hydraulics shop. Highly recommend.

[RaymondR]

My understanding of the need to supply water to the seal via the vent line on the PSS seal was that at above 12 knots the stern tube on some vessels can act like a self bailer sucking all the water out of the tube and causing a dry running and consequently overheating seal.

If the boat will not go fast enough to create a suction in the stern tube and it stays full only a vent to ensure that any air in the tube is vented is required.

I have been doing the lip seal thing in a number of configurations for about seven years now. I have found that they work well until the sharp edge on the lip wears then they leak.

I started with packing but these things require constant attention and with a steel boat where it is desirable to keep as much water out of the boat as possible for maintenance reasons the stuffing box was a constant headache.

I have just purchased a PSS seal but have not yet fitted it and will definately be fitting a split type backup ring to ensure the PSS ring cannot move up the shaft if the grub screws loosen.

[DavidBostonWhal]

Same here, I use PSS shaft seals on mine. Citimarine Store has PYI Shaft Seals, in all sizes. Those are my go to guys for shaft seals.