PSS shaft seal

[ssrig]

Due to the recent few shaft seal or shaft issues lately I had a bit of a look at mine and why I did is the talk about burping the PSS. I thought I had a PSS shaft seal and sitting in my living room right now I am 96.5% sure that it is a PSS but looking online I havent seen one like mine simply because it has two water hoses connected to it!

attachment=0]IMG_1581.JPG[/attachment]

One is connected to a raw water thru hull and the other to the oil cooler and then to the impeller etc.
With this I assume that it doesn't need burping as water is flowing through it once the engine is running.
Still looking online for one similar but no luck yet.

[ssrig]

It just did not make sense so I went back down to the boat for a better look, laying down across the motor and batteries because its all under the muffler, with a big flashlight I see that there is a hose fitting on the log and not part of the PSS.
Not sure if I have ever seen a set up like this, is it common?

IMG_1842.JPG

Also the hose from the most forward fitting on the PSS goes to the port side of the engine, I need to look at the engine manual to see what that is.

[tribologist]

If you read the manual for the pps you will find that for higher speed applications you need to pump in water into the seal to ensure cooling of it. Most A25’s has trouble getting up on the plane so it will not risk running dry so all you really need is a vent line allowing it to fill. The vent shall go up a bit above the water line and not have traps in it preventing water to enter. What you have is probably perfectly fine if you like to keep it as is.

The seal you have is identical to mine and that is a pps dripless according to the paperwork.

Ulf

Ulf

[ssrig]

Thanks Ulf, the line is under pressure from the heat exchanger, so my understanding is that the raw water flows from the heat exchanger to the forward hose fitting on the PSS then flows aft and out the log fitting and out of the boat through a through hull. I have no paper work for the PSS so thanks for that info, good to know when I'm on a plane that the PSS will work!
Gives me the eebie jeebies to look at that un accessable fitting down under there as my muffler and shelf for it make it hard to even see.

[tribologist]

Thinking about it... Personally I would remove it and just run a hose up along the bilge pump hose. (Assuming the bilge pump is right next to it.) If that plastic hose fitting fail you are pumping water into the boat vs leaking it in past the cutlass bearing...

[ssrig]

Something to think about, but for now most everything stays the same as it has been working five or six years, but that area needs a good look at.

[TorreyWP]

Its been my understanding that the "burping" is really only required at initial launch. While hauled, air gets into the seal area and does not easily purge out. Pulling back the bellows for a second and letting some water squirt out, effectively purges (burps) all the air from the seal so it can be properly cooled.

[Mainer]

SSRIG, you have an interesting configuration of shaft log and pss hoses.

My understanding of shaft logs without pss is that raw water comes up through the cutlass bearing and along the propeller shaft to the packing gland, which is then adjusted to drip small amounts of water to maintain the cooling of the shaft.

When a dripless shaft seal is installed, its bellows attach to the shaft log in place of the packing gland. Therefore, the raw water is then coming into the dripless shaft seal bellows. Instructions from the PSS folks will tell you that there is no need to supply lubrication water to the shaft seal UNLESS the boat exceeds certain speeds. My recollection is that those speeds are around 13 knots. Instead, PSS tells you that attaching a hose to the dripless shaft seal will allow any excess water to drain into the bilge.

My A27 has had a pss dripless shaft seal with 4 foot hose routed to the bilge for years, and I've seldom seen any water come out.

Therefore, given the natural path of raw water along the shaft from the propeller forward, your shaft log hose may have been designed to take excess water from the shaft log to the engine, rather than vice versa.

In any case, if your cutlass bearing and shaft log are properly installed, and your dripless shaft seal is also properly installed, there should be no need for a hose running from the shaft log to your engine. Rather the only hose should be running off the dripless shaft seal as PSS describes.

Having said all that, the old adage may apply: If it ain't broke, don't fix it. Good luck.

Dick

[ssrig]

It is an interesting set up on my boat and the jury is still out on the quality of the engine install, I get the impression that the fellow that paid to have the new engine put in had false hopes of expectation for high speed from this boat?
Your understanding of how the water flows is like mine so that makes this set up reverse of what up until a few days ago was how I thought it did flow, even bought an inline raw water filter leading to what I thought was the inflow for the PSS, that inflow was from a seacock I thought but now reversed it flow out that sea cock. So...... raw water in the heat exchanger which is under pressure flows to the PSS which eliminated the need to burp it, then flows aft through the PSS to the fitting on the log and out the thru hull, hopefully. I feel a clash of water happening in that PSS!

The thru hull is in this pic between the muffler and fuel filter and next to one of the transducers.

IMG_1473.JPG

The short time I operated the boat there was alot of water flowing out from the PSS so I have re worked that by compressing the bellows to spec and re facing the mating surfaces so we will see next year what happens but I get the feeling that I will be re doing this system.


I was just going to post the message above and was looking at this picture:

IMG_1596.JPG

Which is the only picture I have of the area under the muff and its a crappy one! But I noticed in this pic the shut off valve that is coming from the exchanger, so could it be that once the boat is launched with the engine running the PSS gets filled with water then, once filled shut that valve off and let the water flow where it wants to, or even regulate the flow from the exchanger with that valve in case it over heats, or.....?

[Mainer]

Just read your note. I can't imagine anyone would install a water line from the heat exchanger to a PSS shaft seal or the shaft log for our type (under 13 knots) application. My opinion is that this is simply a mistake by the installer not understanding how a PSS operates.

Again my opinion: This water line from heat exchanger to PSS shaft seal or shaft log should be eliminated. Also, neither the PSS nor the shaft log should have any connection to incoming water flow. A seacock is not intended to flow water out, only in, so you have two incoming water sources, one from the heat exchanger, and the other from the seacock. The only PSS that needs any incoming water source is one used in a higher speed vessel. I will add that if the hose on the PSS was connected to a raw water source (seacock) it would not cause any problems - just not necessary for our boat speeds. The more open seacocks the higher the risk of leaks that could sink a boat.

I'm quite confident my advice is correct, but also suggest you call PYI, Inc. who is the manufacturer of the dripless shaft seal, describe this arrangement to one of their technicians and seek his advice.

Best wishes for getting to the bottom of this unusual setup and correcting where appropriate.

Dick

[ssrig]

Thanks Dick, I think you are right and I agree with you, mistake or thinking that this boat was going to do 15-20 knots! It seems too weird the way it is set up and I think burping the PSS would be the only reason for it. I like "keep it simple" and will eventually do that here but it sure is interesting figuring out some of the things that prior owners do or what they were thinking. The man had some cash to burn doing the install of the engine!