Propeller shaft seal

[amxr39]

While cleaning up the bilges yesterday, I found a fair amount of residue from the propeller shaft seal. It was more than I expected for only 500 hours at low rpm, around 1600 or less.
Is what I show in the photo normal?
Do you keep a spare shaft seal on hand, just in case? We’re headed to the Bahamas.
Thanks.
Mike

 

[Mac2]

Confirming 500 hours on the shaft seal? Looks like a PSS shaft seal. The carbon seal that rests against the stainless rotor is designed to wear to create a watertight seal. I would expect some black dust for the initial wear. After that, if you’re getting black dust, you have something out of alignment that is creating a wobble. Bad motor mount, or cutlass bearing would be at the top of my list to check. Can you see any wobble? You could make your own gauge by taping a piece of plastic or wood (kabob stick) at a right angle to the stainless rotor. Use about a 1/8 inch gap. This will give you a reference to check for wobble. Next would be verifying shaft alignment with the feeler gauge technique.

 

[Gdavid]

I would also check the adjustment of the forward collar which sets the compression load the bellows provides for the seal. I have seen cases where this collar did not move, but the shaft shifted forward in within the split coupling at the transmission. PSS provides a guide for how much the bellows should be compressed compared to its relaxed state (something like 3/4" to 1"). You would have to loosen the set screws on the foward collar to check this, but I would start inspecting closely for any signs that components have moved (including the split coupling).

Failed motor mounts or poor alignment will cause leaks too.

 

[Mac2]

As some have mentioned, be warned set screws have been stacked in some installations.

 

[amxr39]

My question was, is this amount of dust normal for 509 hours in a year old boat?

 

[Gdavid]

My question was, is this amount of dust normal for 509 hours in a year old boat?

No, should run clean. Would excuse some dust in the first 20 hours of a new seal but it should not be leaving that mess.

 

[Bmarler]

Is this the first inspection of the seal? If so, clean the space and run again to see if it’s still doing it. It’s common for those to make a little schmutz that easily wipes off, but shouldn’t make a line across the bilge like that.

 

[SteveK]

OK, I have not had a PSS shaft seal.
But I have had that raw water hose into the stuffing box. If the dust is dry, is that normal? I would expect some lubrication to the seal and if shaft is wobbling also some water leaking out.

 

[KMAL]

My question was, is this amount of dust normal for 509 hours in a year old boat?

Looks like the bilge on my last two boats - both PSS - looks normal to me...

 

[Helmsman]

Happened on mine at first after delivery. Then no further problem. Cleaned up the stripe, and has been fine.

A couple of things to look at:

Look for water in the bilge. If there isn’t any, then you are past it. Look at the raw water hose where it attaches to the shaft seal, to make sure no water there.

 

[DDW]

Another thing can happen with a PSS. The carbon ring will stick to the SS if it sits awhile without rotating. This has two effects: it jerks the bellows a bit the instant it is put into gear to break it loose, and second, there is some roughness or corrosion or something that takes a short while to polish away. It will sling a bit of water and crud until it is clean again. If you leave the boat for say a month, the best practice is to rotate it by hand before putting it in gear which helps some. Grab the end of the bellows with the carbon bearing surface and twist it back an forth a little. You can feel it break free.

 

[CaptDH]

PSS has some of the best tech support in the industry. Call them 425-400-1772.
I recently replaced my seal and Eric there was amazing. Meanwhile, except after a short break-in period you should not see that stripe in the bilge. Clean it and if it comes back you can adjust the tension and fix it. Call the tech folks so you get the best info.

 

[GeoStr]

My question was, is this amount of dust normal for 509 hours in a year old boat?

If you have only looked at it once in 500 hours it might have been the first 10 or 20 hours that the carbon dust appeared. Perfectly normal in several of my boats with PSS seals. Clean and check again in 5 or 10 hours. Leaking water is more important.

 

[amxr39]

If you have only looked at it once in 500 hours it might have been the first 10 or 20 hours that the carbon dust appeared. Perfectly normal in several of my boats with PSS seals. Clean and check again in 5 or 10 hours. Leaking water is more important.

There is a large inspection window in the deck directly above the seal so it has been looked at several times. We keep our bilge spotless, so we have cleaned it a few times. We just traveled about 1200 miles in about 45 days and noticed this.

 

[GeoStr]

Leaking water is more important, but contact PSS directly if you are concerned. I found them very helpful.

 

[mijmoto]

I have a PSS that we have never been able to seal. I always have the stripe and I am done with the PSS. Swapping to Tides to hopefully acheive a dry bilge. I have been through all of the aspects that cause the seal to leak. I have had a very well known, prorfessional yard work on it three times to no avail. KK installs Tides as a matter of course on new boats so maybe they know something that I don't. Yard sez that there are some boats that always have a telltale black stripe that can't be adjusted out. There has to be an explanation but i am done looking for it. Tides is in process as I write. Jim

 

[Chief Jim]

PSS has some of the best tech support in the industry. Call them 425-400-1772.
I recently replaced my seal and Eric there was amazing. Meanwhile, except after a short break-in period you should not see that stripe in the bilge. Clean it and if it comes back you can adjust the tension and fix it. Call the tech folks so you get the best info.

If your sealing element comes apart it may be lack of cooling lube water. When you talk to tech support ask about installing Slade G 3300 packing and how to do it.

 

[chanprr]

Mike: Small amounts of black dust and spray are normal. The bellows wears and therefore the dust. The water drip means that the bellows prop shaft coupling surface is being lubricated.
I burp the bellows once in a while by quickly compressing the front end to stern, and wipe the bellows surface. That keeps the black dust to a minimum. The bit of water in the bilge from the drip is cleaned out periodically. That tells me the lubricating water is flowing.
Carry a spare if you think necessary. I don't .
A pix of the PSS on my H46 after 10 months and 325 hrs.

 

[Steve DAntonio]

If set up properly these should not shed dust. One sensitivity with face seals is the shaft must be centered in and parallel with he shaft log. If it's not, the rotor and stator will not be parallel, which can lead to leaking and wear. More here Keeping Your Bilge Dry with Dripless Stuffing Boxes | Steve D'Antonio Marine Consulting

The set screws on the rotor SHOULD be double stacked.

What temperature is the black, carbon stator running at? It should be no more than about 40F over seawater temp, and usually much less.

 

[chanprr]

Thanks Steve. Appreciate the feedback.

 

[DDW]

The amount the engine moves makes a difference too. If the engine is on soft mounts, or if the distance from the transmission to seal is short, you get more eccentric movement on the seal face.

 

[Arc]

That is not unusual. Clean the area and monitor. Mine did that for 1200 hours. I called PSS and they agreed it was not a problem.

 

[BB-marine]

PSS or Packless Seal System better known in the industrial world as mechanical seals are good seals better than packing if installed properly. The longevity will out last and out seal packing if installed correctly. Properly and correctly are the key words to longevity. I have installed 100's of these in refineries. 50 years ago most pumps used in refineries and chemical plants used packing shaft seals. The cost of pump down time, and maintenance repair plus environmental fines because of VOC (Volatile Organic Compound) leaks from packing. Pump seals were replaced with mechanical seals and proved to be a superior seal when compared to packing. The same design seals are used in the marine industry. PYI seals function the same way as an industrial mechanical seal. It is a simple concept. Two perfectly flat surfaces with a highly polished surface are pressed together with a specifically designed ( specification of preload) This set preload is the key to proper sealing and longevity. The polished surfaces when installed MUST BE CLEAN ! before the surfaces contact each other they must be wiped clean with no finger prints, grease, oil, dust...... Any contamination can cause abrasion to the surfaces. There is a hard face stainless steel and rotates with the prop shaft and there is a soft face which is carbon composite (stationary attached the the shaft log by hose and clamps. The carbon is the black crap that is seen in your photo. There is a seal flush installed that helps keep the seal cool and flush contaminates from building up around the two seal faces. The seal will last thousands of hours if the seal faces are kept clean and the proper preload is maintained. A contaminated seal face will reduce the longevity. Improperly loaded seal will reduce the seal life. Too much preload will cause excessive wear to the carbon face. To little preload will cause the seal to leak and also damage the sealing surfaces because of contaminants from seawater. I shaft misalignment or a shaft runout out of spec will also reduce the longevity because this will cause the seal faces to run out of parallel.

IMO when carbon deposits are seen there is an issue with the install. The black crap is from the soft face (carbon face) when carbon deposits are seen this is stationary seal material being removed. If the surfaces are clean, running parallel, preloaded correctly, cooled properly from the flush there is no reason for wear. The only reason I can think of for a PSS seal representative to say it is normal to see carbon deposits visual around the seal area in the bilge is (It is common to see after a new install because the installer may have not cleaned the faces properly and the contaminate caused some premature wear to a portion of the flat surface.) As long as this wear does not run horizontally across the entire flat surface the seal will function and seal.

If I had a PSS seal that I continually saw carbon wear rings in my bilge I would inspect the carbon ring for damage. If the carbon or hard face has scratches uneven surfaces it should be replaced. If the carbon and hard face looks good then reset the seal preload. Clean area and inspect for wear. There should not be excessive wear if the seal is clean and preloaded properly.

 

[capran]

While cleaning up the bilges yesterday, I found a fair amount of residue from the propeller shaft seal. It was more than I expected for only 500 hours at low rpm, around 1600 or less.
Is what I show in the photo normal?
Do you keep a spare shaft seal on hand, just in case? We’re headed to the Bahamas.
Thanks.
Mike

Depending on how far into the Bahamas, spares are never a bad idea. Is this the first time you have looked at the area in 500 hours? We had new dripless installed when we bought our 2008 Helmsman 38 aka Seville and after 4 summers cruising have about 500 hours. But I check mine every time I'm in the bilge, which is several times a week, and we wipe up the little bit of dust that might appear, so I have no idea if it would look that heavy had I not kept up on it.