PSS shaft seal installation

[a64pilot]

They may likely be like me, just from way back remember too many Green Monster stories.
Volvo got decently popular back in the 70's and came out with some neat stuff like counter rotating props, but if anything broke, you were on your own, and if you could get parts, they were likely marked up for or five times before you got to buy them, cause they were outrageously expensive.
Just based on what I remember as a kid, I will never have a green motor if I can help it, although I am sure many are fine

[senormechanico]

Having had two PSS seals on two boats, I like them.
Imho, the replacement schedule is a big bunch of CYA for the mfr.
The factory replacement schedule for my boat's waterstays is every five years.
The factory has to be notified if you want to order them because they don't even stock them and the price is somewhere North of FIVE THOUSAND DOLLARS USD ! That's three bucks a day, whether or not I'm sailing the boat !
Mine are original from 1995 and still looking good in the rainy PNW.
Factory's CYA, anyone?
Now having said that, I'll let you all know if anything lets go.

[emcmia]

Originally Posted by a64pilot

I won't go into too much detail, but I am about to get tired of mucking with my stuffing box and thinking can the thing and go with a PSS shaft seal.
However I don't want to pay for a haul and I can't see as how doing it in the water would be that bad.
Anyone installed one with boat in the water?

My cat came fitted with Volvo dripless seals, both of which I replaced with PSS seals, while afloat, 15 years ago. Stuffed rags in stern tube from interior to reduce flow, which was sufficient. Just make sure shaft is clean and smooth prior to installation. Periodic adjustment and O'ring replacement is needed to eliminate/minimize leaking. Bellows are rugged (i.e. well made) and have never given me pause.

[boatbod]

Personally I find the PSS to be a maintenance hog, especially if the shaft has any wobble whatsoever.

Aside from that, feel free to install it with the boat in the water, assuming you can:
- remove the shaft from the coupling without having to use a slide hammer
- move the shaft sufficiently far aft to get the old siding box off and the new PSS on. Usual limitations are the prop coming up hard against the rudder, or the shaft zinc hitting the strut.
- have a large enough bilge pump to handle the water ingress.
- have a means to temporarily seal the shaft log when things inevitably go wrong.

Good luck...

[cpt_757]

I supposed to replace my stuffing box last year but could not make my haul out time since my schedule conflict. Then boat yard were so busy, now I will do mine since the repack did not work well.
PSS requires make a hole to the hull since it uses water to lube the system. Need haul out, definitely.

[a64pilot]

Originally Posted by boatbod

Personally I find the PSS to be a maintenance hog, especially if the shaft has any wobble whatsoever.

Aside from that, feel free to install it with the boat in the water, assuming you can:
- remove the shaft from the coupling without having to use a slide hammer
- move the shaft sufficiently far aft to get the old siding box off and the new PSS on. Usual limitations are the prop coming up hard against the rudder, or the shaft zinc hitting the strut.
- have a large enough bilge pump to handle the water ingress.
- have a means to temporarily seal the shaft log when things inevitably go wrong.

Good luck...

I have the above covered, but will likely just buy one, put it in spares and do it next haul out.

You do not have to add another hole in the boat. Although not required, I will likely plumb the vent into the raw water cooling of the engine, so that engine running, water is pumped through the seal and out through the Cutlass

[emcmia]

You may want to review the installation instructions on the PSS website. In the Plumbing section, they indicate externally supplied water is not required on sailboats and displacement hulls with speeds less than 12 kts.

[a64pilot]

It is heavily recommended for boats that have the cutlass in the shaft log

[GILow]

Originally Posted by cpt_757

I
PSS requires make a hole to the hull since it uses water to lube the system. Need haul out, definitely.

This is not correct.

As stated by others, low speed use (such as seen with steady old monohull cruising yachts) merely requires the hose from the PSS is taken to a safe point well above the waterline to allow the PSS to breathe.

A64 is thinking of plumbing his in to the raw water cooling circuit... well, each to their own but I personally did not do that because I like to keep things simple, particularly when it comes to cooling systems and anything that might flood the boat if it fails. I really see no advantage in making things more complicated than they need to be. We have a top speed under engine of 8 knots, which is well below the speed where the PSS requires forced water flow for cooling.

[GILow]

Originally Posted by a64pilot

It is heavily recommended for boats that have the cutlass in the shaft log

I believe it depends on the style of cutlass. Our 1.5" shaft has huge grooves in the forward cutlass that allow plenty of water flow. I did a 35 mile, 7 hour trip under engine recently and out of curiosity checked many components regularly including the PSS. There was absolutely no evidence of any heat accumulation in the seal.

That was at 1150 rpm on the engine, so about 770 rpm on the drive shaft.

[a64pilot]

Call PSS, I did, both they and Lasdrop recommend forced water cooling if your Cutlass is in the shaft log.
For PSS talk to Kenneth Planck

[GILow]

Originally Posted by a64pilot

Call PSS, I did, both they and Lasdrop recommend forced water cooling if your Cutlass is in the shaft log.
For PSS talk to Kenneth Planck

I understand why they do this. They are, correctly, covering the worst case scenario of a cutlass that restricts water flow to the point that the seal overheats or runs dry.

But to my mind, it is a matter of cascading risks. I, personally, felt the risk brought about by the added complexity of tapping into the raw water cooling and forcing water into the seal chamber was much greater than the risk of the seal running dry or becoming hot from inadequate thermally induced water exchange.

It is simple to see if there is adequate water exchange in the seal, by running the system at normal operating speed and checking the temperature "by hand". (Carefully of course.) I did this for half an hour in the pen initially, no problems, then periodic checks for the first few months. It took nearly three years before I had to run the engine for over half an hour, with the 7 hour trip across the Gulf recently being the first chance I got to test a number of things, including the seal, on a long run.

Another simple test, on my boat, is that even at normal cruising power, I can gently and carefully pull the seal aft and be rewarded with a very high pressure, sustained gush of cold water between the seal faces. So there is plenty of water flow and pressure despite the forward cutlass, but this is obvious when you see the design of the cutlass itself, which was originally conceived as a self lubricating bearing and hence needed to allow plenty of water flow.

Each to their own, but I, for one, do not slavishly follow all manufacturer recommendations when such things might induce other greater risks.

[a64pilot]

See I am not so worried about the seal, I assume that a continuous flow of water may help lubricate the Cutlass and make it last longer, although I concede that with a regular stuffing box, there is no regular flow of water.

[bill good]

a64, I also believe the water flow will help. See my #7 & consider. Although not a venturi, there is a movement of water to lub & cool the seal by the effect of the water flow. Risk of leaks no more than a breather. Also not pressurized from taking it from a pump feed. Very suitable to sail boats IMO. Also found it easier to plumb in by a "T" on the inlet of the engine water circuit! There was a very slight warming of one of mine which went to being cold after installation.

Regards

[GILow]

Well I am confused by this. The installation instructions for faster boats appear to call for positive pressure, either by tapping onto the cooling system before the raw water thermostat (not suitable for fresh water cooled engines like ours) or by fitting a scoop to the skin fitting.

Tapping into the raw water input, to my mind, would imply a very faintly negative pressure.