Manecraft shaft seal

[longjohnsadler]

My relatively new to me boat has one of these.
After recent relaunch, second trip (not first) saw appreciable amount of water ingress at high engine revs, falling to nothing at low revs/engine off. Local mechanic had a look and adjusted rotating seal tighter against stationary seal by means of jubilee clip. Problem seemed to be solved. Later I found tag labelled 'break in emergency only' lying (broken) below the seal.
Just found website that says these seals should need no maintenance, and that under no circumstances should shaft be rotated if emergency clip (protected by emrgency tag) is tight.
Am assuming emergency tag has fallen off without emergency clip being engaged ( I hope)- but not sure why it would let in so much water or need adjusting?
Also I'm assuming it's a lift out to fit new seal..

 

[mireland]

The emergency seal is tagged with a plastic tag to show it has not been tampered with - bit like your electricity meter at home. In essence the emergency seal is just a jubilee clip which you can tighten down onto the prop shaft and so prevent water ingress from the propellor end of things if the rubber seal starts leaking. Of course the seal also takes water from the engine water inlet which is used to lubricate the seal surfaces when it is running. To make the thing watertight you have to close of the engine water intake at the same time as closing off the emergency seal. It is easy to see if the emergency seal is engaged - the jubilee clip has a turn key. Clockwise is lock down so try turning it clockwise and see if it is tight. If it is engaged you would also see the rubber squashed down onto the prop shaft. You cannot engage the emergency seal by accident so it is unlikely it is engaged! As to your leak: It can leak through the two bronze bearing faces if they are not pushed together enough or it can leak because of a split in any part of the rubber. I do not know how old your seal is but I think they are good for 5 years. The bearing surfaces wear away slowly so it may be necessary to push them together harder to compensate. Other possibility is that if you ground and get a load of mud and muck in the rubber seal it can get between the bearing faces and cause some leaking. This happened to mine once. To fix this, gently prise the bearing faces apart with your fingers and let water flow out and into the bilge and flush out all the s---t! The bad news is that it is indeed a lift out to replace the seal. Look here for details of the seal - http://www.tnorrismarine.co.uk/manecraft.php -and download the brochure at the bottom of the page

 

[30boat]

I have one of these seals,in a drawer.I took it off and put in a Volvo shaft seal.Never looked back.The Deep Sea Seal works well enough but is difficult to make totaly watertight.It has to be perfectly square to the shaft(both bits) wich is very difficult to achieve.And compression has to be set with that little blue gauge at the same time.Too much to go wrong if you ask me.And if something falls on it it could become distorted and leak badly enough to sink the boat.On top of all that it's much more expensive than the Volvo.
The downside with the Volvo seal is that it requires a perfect bearing surface on the shaft.

 

[cpedw]

From your description of the symptoms, I think the seal was leaking because of movement of the shaft and seal under load; as the propellor pushes, the shaft moves forward a bit and the part of the seal attached to the shaft is pushing less hard against the other part of the seal that's fixed to the stern tube. If the movement is too much or the seal is not well adjusted, it can start to leak. It sounds like a small adjustment to the seal was made, so that it is pushed together more firmly.
I think there's little doubt the emergency seal has not been engaged, just the tag broken off. If the emergency seal was activated, turning the shaft would rip it off.

Derek
ps I agree that the long term answer is a Volvo seal.

 

[michael_w]

Exactly the same thing happened to me. Worn mounts and prop thrust would open the seal. Nearly sank in the Hamble River. /forums/images/graemlins/blush.gif

Solution? New mounts and an old style packing gland, They may dribble a little, but you won't get a catastrophic flood.