Shaft seals question

[Parabolica]

A question for the learned souls of the YBW forum.

I see many motorboats on the hard for long periods of time and assume by doing so, that the shaft seals, especially those that are up on their hours, contract meaning imminent changing is required before the boats are returned to the water.

Or is there a solution (no pun intended), to stop this happening and keep the glands in good working order ?

 

[Plum]

A question for the learned souls of the YBW forum.

I see many motorboats on the hard for long periods of time and assume by doing so, that the shaft seals, especially those that are up on their hours, contract meaning imminent changing is required before the boats are returned to the water.

Or is there a solution (no pun intended), to stop this happening and keep the glands in good working order ?

What design/make of shaft seal are you refering to. I have never experienced a seal contracting.

Www.solocoastalsailing.co.uk

 

[Tranona]

Most shaft seals are very tolerant of lack of use out of the water and unlikely to need any special attention on launching. Equally hours of use is not a good indicator of any potential problems. One caveat is that face seals can stick together if left un rotated for long periods of time and lip seals should be checked for lubrication.

 

[oldgit]

worth a look.
Stern gear
..............and for the brave the traditional shaft seal packing can be replaced while the boat is in the water.
Need to make sure every last bit of the old packing is removed.
Some boaters have the curious habit of just putting another new circle of packing on top of the existing packing .
This will result in a lot of rock hard old compacted packing inside the gland doing nothing much at all.
A good oppertunity with older boats to visably check on the condition of the surface of the prop shaft inside the gland.
If constantly and frequently repacking does not diminish water entry, pitting on the surface of the shaft inside the gland may be the cause.

 

[Forty_Two]

I have replaced my traditional seal packing in the water a couple of times.

I wrap a tee-shirt tightly round the shaft/gland after unscrewing the gland nut. Very little water comes in in my case. No rush to then remove all the old packing. Luckerly my access is excellent which makes a big difference.

Nice thing is you get the initial adjustment right & only need to revisit when it beds in after a trip or two.

 

[Parabolica]

Thanks all,
So it must just be that mine were time expired. The boat came out onto the hard for some painting to be carried out and when it went back in, 2 months later, water leaked in from around the shaft seals. At this point i had little choice but to accept to have the boat lifted and them changed as an emergency so it is what it is and i have peace of mind that all is good now below the waterline as i had all of the seacocks replaced too.

So i was just curious really but it must be that ny presumptions are just wrong.

 

[Tranona]

What type and make of seals were they? Generally they don't have a fixed life.

 

[Parabolica]

What type and make of seals were they? Generally they don't have a fixed life.

I have no idea. The work was arranged by the Varadero at the marina in Mallorca on my behalf whist i was home in UK.

i can ask. Are there good and bad brands of seal ?

 

[Tranona]

I have no idea. The work was arranged by the Varadero at the marina in Mallorca on my behalf whist i was home in UK.

i can ask. Are there good and bad brands of seal ?

Not really - just different designs. Three basic types. The oldest is what is known as a stuffing box which relies on a water lubricated woven fabric seal wrapped in rings around the shaft within a housing. Adjustable and easy to repack if dried out. Second is similar except that rubber lip seals are used, either in a housing or as part of a rubber moulding - most common is the Volvo type. These can wear but would not normally be damaged by being left out of the water. Require a simple priming process after the boat is launched. Third type is known as a face seal which relies on a foxed disc attached to the stern tube and a rotating disc on the shaft. These can stick together if not in the water, but again a simple recommissioning procedure may bee required.

What type of boat is it?

 

[MapisM]

stuffing box [...]
Adjustable and easy to repack if dried out.

Worth mentioning that they are also the less prone to catastrophic failures.
I'm not suggesting that stuffing boxes are still the best thing since sliced bread, mind.
But they always worked just fine in my previous boat, and they still do now that she's 26yo.
OTOH, nowadays I've got what are possibly the best face seals money can buy (Fluiten), and they are flawless.
That's the thing with modern seals, both lip and face: you'd better not fit anything but the best.
With stuffing boxes, anything goes...

 

[QBhoy]

worth a look.
Stern gear
..............and for the brave the traditional shaft seal packing can be replaced while the boat is in the water.
Need to make sure every last bit of the old packing is removed.
Some boaters have the curious habit of just putting another new circle of packing on top of the existing packing .
This will result in a lot of rock hard old compacted packing inside the gland doing nothing much at all.
A good oppertunity with older boats to visably check on the condition of the surface of the prop shaft inside the gland.
If constantly and frequently repacking does not diminish water entry, pitting on the surface of the shaft inside the gland may be the cause.

Totally agree. All too often, a lazy effort of just the top two strands of packing replaced. I can perhaps understand it if she’s in the water, in an emergency. But ideally it should all be completely replaced. Further more, replaced using the correct method and technique too. Certainly a skill and a craft to doing it properly.