rigger 47 Posted August 5, 2010 Share Posted August 5, 2010 idm28 PostPosted: Sat Feb 28, 2009 10:26 am Post subject: Shaft Seals What are the good shaft seals around these days for a yacht. I believe there is a Kiwi made one. Also are the anti vibration rubber packers any good? I am still looking for a mobile marine mechanic who can get to Gulf Harbour. Does anyone know of anyone? ======================================================================== Tangent PostPosted: Sat Feb 28, 2009 11:57 am Do you need masking tape to shaft a seal? Seriously though, I used Ces Tong (Auckland Marine Servicing) and he supplied a shaft seal of his own design - he apparently helped Henley's develop their seal. Never had a problem with it, keeps the boat completely dry. It uses 2 greased o-rings on the shaft as opposed to a spring loaded ring bearing down on a sealing flange. Ces is mobile and does the full range of engine work and marine engineering (drive trains etc). ======================================================================== wheels PostPosted: Sat Feb 28, 2009 2:45 pm The simple packing seal with gortex is still a very simple and reliable way of sealing the shaft. I have had issues with some of those dripless seals in the past and consider the simple of packing seal to be the best. I don't know the one Tangent is speaking of, so it may be worth taking a good look at it perhaps. "So did you blow a Seal?" "No it's Mayonase" ======================================================================== idm28 PostPosted: Sun Mar 01, 2009 6:13 pm Thanks for the replies. I have now ascertained that the existing seal is a Manecraft brand...has anyone got any knowledge of these or know who the agent is? Still looking for a mobile marine mechanic in Auckland. ======================================================================== wheels PostPosted: Sun Mar 01, 2009 6:32 pm Auckland Engineering supplies are the suppliers. What exactly is wrong with it??? It's possible it just wants a small adjustment as these things are good for 10000 + hrs. Easy to replace though. You should be able to do it yourself. It does mean uncoupling the shaft and a bit of water will squirt out around the shaft, but the pump will keep up with no problem. I'd love to help, but I'm a bit far away. ======================================================================== idm28 PostPosted: Sun Mar 01, 2009 7:30 pm Well its only done about 3,500 hours so maybe I will keep it. I had read somewhere to replace every 5 years and its probably twice that. I think the faces have to have a certain thickness on them as I presume they wear so I will check that. I had trouble with the rubber boot piece slipping on the shaft even with two hose clips so I think a collar of some kind attached to the shaft itself should fix that. I am taking the boat out of the water this weekend so it should be easy to check out. I must say they seem a rather vunerable component in terms of potential failure. Thanks for the reply. Knowing they have a long life span is good news as they are not cheap. ======================================================================== wheels PostPosted: Sun Mar 01, 2009 7:49 pm I have never like any of these so called "dripless" seals. All the designs are similar and all are frought with problems. It is essential water lubrication is supplied to the seal or it will wear very fast. As i said earlier, the simple gland packing system is actually one of the best. However you have it now, so lets keep positive. Water tightness is maintained by the two halves being held together. So if the clips don't keep that half tight on the shaft and it slips, it will come loose enough to leak. It could be worth trying a different clamp. A Donaldson clamp would be a better bet. These are great clamping devices. A wide band with a bolt that pulls it together and creating a heck of a clamping pressure. I use these solely now on all my hoses. Too big to be able to use two clamps, but you will never need to use two clamps. Far supperior. ======================================================================== idm28 PostPosted: Sun Mar 01, 2009 8:41 pm will definately try that..chers ======================================================================== idm28 PostPosted: Sun Mar 01, 2009 8:46 pm This from a boat forum "Volvo Penta dealers sell them. They have a 5 year life and should be changed at the end of 5 years in service. My boat had another well known proprietary type of stern seal but same system of rubber boots mane craft deep sea seal. 6.5 yrs old, Survey said they were OK , I had the shafts drawn a month later to replace cutless bearings and upon inspection the stern seals were perished. I have heard a recent one where a boat sank in the UK due to stern seal failure a rubber boot type and the Insurance company refused to pay the claim in full as the rubber boot stern seals were over 7 years old! Change them at 5 years, dont risk it. " ======================================================================== wheels PostPosted: Mon Mar 02, 2009 5:50 am The manufacturers themselves say that a yearly inspection when you inspect all other things like clips and seacocks and so on is essential. However, they also say the seals have passed 10000hrs in their "test boats". The big issue with rubber is that oil/grease attack it and will perish it. So regular inspection is required. If the seal is good condition, it should be fine. If it is perished, then replacement is required. I doubt the sealing face will wear out. I think the rubber body will let it down before the sealing face does. By the way, it's not actually rubber. It's some exotic material. ======================================================================== wheels PostPosted: Mon Mar 02, 2009 6:16 am This may help. http://www.wartsila.com/Wartsila/global ... ecraft.pdf ======================================================================== Link to post Share on other sites
John B 106 Posted August 5, 2010 Share Posted August 5, 2010 Thanks Rigger, I wish I'd seen this 2 weeks ago, it would have saved me some grief. AES did help me out with a new manecraft seal but whats happened with them is that Wartsilia has just doubled the price of all their seals. My seal ,which was $900 plus tax 6 months ago is now $2k rounded.( plus) As I said on my thread, even a hardened marine consumer like me balks at that . Anyway , for what its worth I see two general types of seals on the market. Lip seals and face seals. The lip seals have a lip of special 'rubber' which is touching the shaft and creating the seal. On a lip seal the lip touchs the shaft and the shaft spins against it. Face seals have two faces compressed together by 'bellows' . A manecraft seal has a bronze face meeting a composite face for example. A Pss seal has a carbon face meeting something else. In other words .. a hard face and a wear face, one spinning against the other at shaft speed. Chatfields have a lovely looking and well made lip seal type with a back up of a standard grease stuffing box for emergency. At least one lip seal type requires an extra bearing at the seal end of the shaft log. I think thats the kiwi seal, but maybe they all do. What strikes me is that lip seal types may well be very good units but would probably suit a new installation where face seals seem to me to have more tolerance and are more forgiving for an older or existing installation. But I'd listen to an expert opinion on that. Link to post Share on other sites
rigger 47 Posted August 5, 2010 Author Share Posted August 5, 2010 there are a few other type of shaft seals - I'll leave those that know their stuff to describe them. AES are a good bunch - we get a fair bit of stuff through them. Link to post Share on other sites
Guest Posted September 2, 2010 Share Posted September 2, 2010 Face seals are good if all the flex engine mounts are ok. if one or more mount starts to fail the engine can drag the prop shaft out of centre resulting in less pressure on the seal face. if ignored the seal will eventually leak. Fortuneately I have found they only leak when motoring - bucket loads. On the other hand lip seals units move with the shaft. Still, dont ignore a vibrating engine! I also like the traditional stuffing box, particularly at the end of a length of hose. the hose being secured to the stern tube - good qual hose and clamps of course! Link to post Share on other sites
John B 106 Posted September 2, 2010 Share Posted September 2, 2010 I'm not sure I agree with that Weta. I see face seals as more tolerant of movement and when I think about it thats backed up by the fact that the lip seal manufacturers insist on an extra bearing at the seal end of the shaft log, to restrict the shaft movement or flex. I also look at the contact surfaces on a face seal.. about 6 mm? on the manecraft, pressed against a flat bronze face of about 12 mm I seem to recall, where a lip seal has about what .. 1 or2 mm contact against a revolving shaft. Link to post Share on other sites
Recommended Posts
Archived
This topic is now archived and is closed to further replies.