Dripless shaft seal maintenance

Meriachee · Nov 15, 2015

The reason for the hose is to be able to bleed off any air that might get in there. You can get air entering the tube from any cavitation that may happen in reverse. If you lose the water contact with the mating surfaces of the stainless and carbon parts, they say that they will heat up and wear quickly.
If you're thinking about replacing the bellows, consider upgrading the carbon ring to one that's vented.

uncledom · Nov 16, 2015

Like Meriachee said it's really about ensuring the seal doesn't get air bound. The vented version ensures this. I would change the whole thing myself but at least change the belows for safety. Just my two cents.

31seahorse · Nov 16, 2015

Hello Charlie98117,
When air builds up in the older style dripless seal they can be "burped" by pushing the graphite ring aft from against the stainless steel collar. A bit of water squirts in and the air is out. I have done that from time to time on an older model seal. That seal became hot and began to squeal (One of those "what the %#LL is that noise sounds!") when air entered the hull tube. That happened on our boat in a following sea. The old seal on our boat had begun to wear oddly......the graphite was thicker on one side than the other....perhaps a bit of misalignment there too?

Anyway, if your dripless seal is 20? years old I think you would be wise to change the entire seal. The cost is in the neighborhood of $350 for the entire replacement. Good instructions came with the PSS models I have installed, and I was successful in the correct placement of the collars by using the measurements provided. I'm not sure you could buy just parts of it, and with the effort required to change part of it you might as well replace the entire seal while the boat is out of the water. In preparation for that change you might consider using a penetrating oil on the bolts of the shaft coupling and on the mating surface of the shaft coupling in order to help with removal.

RoyS · Nov 16, 2015

I have one of these as well. First of all, mine also had no bleed tube. I decided to replace the bellows only and ordered a replacement. After examining the assembly, I found no reason to change anything else. Furthermore, the removed bellows looked as good as new after ten years of service. There were no cracks or deterioration of the rubber visible under close examination. I burp the unit every spring and that seems to work fine. Removing the prop shaft in my case was extremely difficult. Good luck with that. My experience with this unit would indicate that the PYI recommendation of four years life expectancy for the rubber bellows part is overkill. Yours has been in service 20 years and mine 10 years. Unfortunately the only way you can more accurately determine a suitable replacement interval is to wait for a failure and then dial back from that. Of course, you might sacrifice your boat in that experiment.

JamesG161 · Nov 16, 2015

The good news is that every time you go from Forward to Reverse you fill ( albeit partially), the non vented bellows. The water is to friction cool the Carbon rotary seal surfacc, not a lot of heat generatedfrom less than 12 knots. Looks like the non-vented worked well for you. Also at the berth, the air will slowly dissolve in water and the sea slowly fills the bellows. The seal does (drip, drip , drip) but the bellows contain it.

The Bellows act as a seal compression spring. Follow their bellows compression % closely. You should measure the static bellow "end to end" distance to the "millimeter" when new. Significant change in that distance shows seal wear, maybe failure and bellow's fatigue.
It is a good product for me, so far.
Jim...

dlochner · Nov 16, 2015

Yes, it is time to replace the bellows, but you might as well replace the whole unit. A bellows alone will cost about $80 and you still have the unvented seal. The graphite ring may also be worn. Some PO of my boat may have used a screwdriver to burp the bellows leaving deep scratches and gouges in the ring. So we replaced the whole unit.

Also, once the new seal is installed add a shaft collar to prevent the Seal collar from moving if the set screws loosen. See these from McMaster-Carr: http://www.mcmaster.com/#shaft-collars/=zu4dn3

seadaddler · Nov 16, 2015

I replaced my bellows few years ago and went to Mainsails web page and he shows great
info how to take apart the shaft coupling and mine was 2007 and did use small torch with heat to help come apart and lots of soaking PB blaster.
I also added bottle at end of vent tube up high.
Nick

sesmith · Nov 16, 2015

The vented version will take up a little more space than your unvented one. I just replaced mine a week ago, and went with the vented design because I had issues at times with the unvented one trapping air, and having to be burped at the most inconvenient times. As can be seen from the pic below, the vented version just fits my boat, and it was a challenge to get things back together in that space.

Concerning your coupling, read Maine sail's info on that before you do the upgrade. You will likely need a new coupling, and a machine shop fit of the coupling to your shaft (and possibly a new shaft). You may want to do the cutless bearing at the same time, and will need to realign the motor when you're done. I needed a shaft, coupling, and cutless bearing on my boat this summer. Just did the seal, as we couldn't get one at the time I had to do the other work.

A couple of helpful links from the Main sail (compass marine collection):

https://marinehowto.com/installing-a-pss-shaft-seal/

https://marinehowto.com/new-prop-shaft/

Meriachee · Nov 16, 2015

A split coupler is the way to go if that road is being taken.

Dripless shaft seal maintenance

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