Propshaft seal

[BobnLesley]

Our new boat's got a seal/stuffing box as shown in the attached photo:

It drips at a rate of about one drip per second - not a problem in itself, the bilge will hold 3 months worth of drips, but even when I squeeze in some grease, it doesn't significantly slow down, so I assume that the packing needs either tightening down, or replacing?

The collar at the front appears to be one pice (hex for spanner at either end) and is screwed onto the boss behind. It's not eager to move in either direction, though it's almost fully tight - no more than 2 or 3 threads showing - so I'm assuming that it's fully adjusted and needs a re-pack? I can/will do this when we haul out in a couple of months, but in advance, I would appreciate any input from people with the same sort of unit

 

[jerram]

Have a look at http://www.diybob.com/diyPackingGland.htm and http://www.tb-training.co.uk/10sgear.htm

 

[Tranona]

Straight forward(if a bit messy) job if you follow those instructions. The grease is not really needed for the seal, which is made by the packing on the shaft. However, it needs to be "wet" so that it runs cool. Inspect the rubber connection carefully as it may need replacing as well - it is a special type, not ordinary rubber hose.

If you are taking it apart you may want to consider replacing it with a modern non-drip seal. Variety of different types on the market.

 

[ghostlymoron]

I think the collar at the front is likely to be splittable as the flats at the two ends don't line up. Don't know if that makes any difference to your query though. A 'side-on' photo would make it easier to identify the type of unit it is. Normally i would refer you to Vyv Cox's website 'coxengineering' for a good source of info on sternglands but he is having trouble with his photo gallery at the moment. Her's a picture of mine http://s496.photobucket.com/albums/rr330/ghostlymoron/?action=view&current=IMGP0335.jpg rather messy! But it looks basically the same as your's except that it has 'C' spanner flanges rather than flat hex's. The left hand 'C' is on a cup containing the packing and the right hand one is a lock nut. You'll need to back off the locknut before you can unscrew the cup. You'll need some big spanners!
IMHO the greaser is a waste of time as the grease goes down the stern tube rather than into the packing.

 

[neil_s]

If you've got 2 or 3 threads still to go you should have plenty of adjustment. My seal needs adjustment every two years or so and about 1/8 to 1/4 turn is sufficient to reduce the drips to one a minute. You need two spanners to fit - one for the locknut at the back and one for the gland nut itself. It's not necessary to do the nuts up tight - lightweight spanners cut from thin plate should be OK. Note that an occasional drip is necessary with this type of seal.

Neil

 

[BobnLesley]

Thanks for the replies!

sorry I was so long in coming back to say so; we’ve been away from decent/inexpensive internet access for a while and busy getting battered by heavy weather and repairing the damage. Ah, the joys of sailing!
My initial thoughts too had been to just junk the unit and replace it with a modern deep-water seal; the sort of thing we had on our last boat and which we better understand. However, our current plans will take we somewhat off the beaten track and a Surveyor commented – we think wisely: “What you’ve got might drip a bit, but with your deep bilge, you can ignore that. What’s more important to consider is that even a major failure would only mean that you might get a couple of gallons a day coming through and you’ll still be able to use the engine. A major failure on one of the modern seals will often require you to shut/seal it down completely, so you’d have no engine drive until you’ve found and got to somewhere to haul out and repair it; also you’ll have to carry at least one complete spare unit too; parts are unlikely to be available outside the major yachting centres.”
As I said, it sounds pragmatic advice, so we’ll probably make the best job we can of repacking/sealing it when we haul out and just learn to live with the drips.

 

[Conachair]

A major failure on one of the modern seals will often require you to shut/seal it down completely, so you’d have no engine drive until you’ve found and got to somewhere to haul out and repair it; also you’ll have to carry at least one complete spare unit too; parts are unlikely to be available outside the major yachting centres.”
As I said, it sounds pragmatic advice, so we’ll probably make the best job we can of repacking/sealing it when we haul out and just learn to live with the drips.

Agree with keeping it simple, one less thing to mave in the back of your mind.

This stuff worked well for me, no drips for about 5 years, if you can get your hands on it.
http://www.asap-supplies.com/marine/ptfe-flax-gland-packing

 

[Tranona]

sorry I was so long in coming back to say so; we’ve been away from decent/inexpensive internet access for a while and busy getting battered by heavy weather and repairing the damage. Ah, the joys of sailing!
My initial thoughts too had been to just junk the unit and replace it with a modern deep-water seal; the sort of thing we had on our last boat and which we better understand. However, our current plans will take we somewhat off the beaten track and a Surveyor commented – we think wisely: “What you’ve got might drip a bit, but with your deep bilge, you can ignore that. What’s more important to consider is that even a major failure would only mean that you might get a couple of gallons a day coming through and you’ll still be able to use the engine. A major failure on one of the modern seals will often require you to shut/seal it down completely, so you’d have no engine drive until you’ve found and got to somewhere to haul out and repair it; also you’ll have to carry at least one complete spare unit too; parts are unlikely to be available outside the major yachting centres.”
As I said, it sounds pragmatic advice, so we’ll probably make the best job we can of repacking/sealing it when we haul out and just learn to live with the drips.

Suggest your surveyor has not got a clue about modern seals. The only design that will do what he says is the Manecraft or Deep Sea seal - which few people fit for the reason he states.

None of what he says is true of the 3 main alternatives, Volvo/Radice one piece seal, Tides Marine lip seals and PSS face seals. While they have differences and some people prefer one design to another, they all do what they say and are superior to a stuffing box. Having said that, a good stuffing box, well maintained is also perfectly adequate - just that many leak, they can be messy and not all are maintained properly. If your existing stuffing box needs repacking and the hose replacing, it is well worth considering replacing it - particularly (as is often the case) the shaft is worn as well.

 

[Spyro]

If the rubber hose on your traditional stuffing box gives up you will get more than a few gallons a day. Having said that if you replace the hose with the proper type it will last for years and years