Packing gland

[dash72]

My stern gear consists of a packing gland that has a flanged compression sleeve that is tightened by two nuts on studs. It appears to only take two loops of packing. Behind it is a rubber tube attached to the stern tube by jubilee clips and torque protected by castellations in both stern and gland tubes. Attached to the stern tube at the rear of the rubber tube is a remote greaser. My problem is that I have seen a similar set up with a water feed from the engine rather than the greaser. I'm not sure whether mine is set up right as the grease seems to enter the stern tube about 100mm from the packing. How does the water feed work? What happens when the prop is spinning while sailing without the engine water feed? Any answers would be much appreciated as I'm installing a new engine and want to get things right.

 

[Tranona]

Nothing wrong with your current gland except they are usually messy and leak. If you are replacing your engine suggest you ditch it and replace with a modern dripless seal. There are several different types, the simplest and cheapest being the Volvo or Radice seals.

Regular topic on here and a search will find many threads, latest lower down this page.

 

[vyv_cox]

Yes, as Tranona says that is a common arrangement. Have a look at my website under 'stern gear' for photos of various types, courtesy many posters here. The grease entry you describe is common. It seems the grease floats up the stern tube where it just might do some good between packing and shaft.

 

[dash72]

Nothing wrong with your current gland except they are usually messy and leak. If you are replacing your engine suggest you ditch it and replace with a modern dripless seal. There are several different types, the simplest and cheapest being the Volvo or Radice seals.

Regular topic on here and a search will find many threads, latest lower down this page.

Have had a look at Volvo seals and worry about them failing when I'm not there to do anything about it. Not really sure how fast water comes in when it does fail. I know you can keep a spare on the shaft to replace it without getting the boat out of the water. Deep sea seals scare me to death but they seem to work ok even with the shaft out of line. I've heard that the PTFE type packing is pretty good and hardly lets in any water.

Thanks, will have a look at other threads.

 

[dash72]

Had a look at your website http://coxengineering.sharepoint.com when trawling before I tried the forum. On ours the grease has to float a bit of a distance before it hits the packing but I assume that's how it works.
Very interesting site by the way and thanks for your reply.

 

[Tranona]

Have had a look at Volvo seals and worry about them failing when I'm not there to do anything about it. Not really sure how fast water comes in when it does fail. I know you can keep a spare on the shaft to replace it without getting the boat out of the water. Deep sea seals scare me to death but they seem to work ok even with the shaft out of line. I've heard that the PTFE type packing is pretty good and hardly lets in any water.

Thanks, will have a look at other threads.

Think you are confusing the Volvo type seal with the Tides. On the Volvo the 2 seals are part of the moldings. They are very reliable, fitted on thousands of Beneteau, Jeanneau and other boats. Do not fail catastrophically but the seals may weep at high usage, particularly in sandy water. However no different from any other seal and plenty of warning of potential wear.

 

[nemodreams]

There are lots of variations - on the standard stern tube set up.

Mine is the simplest and oldest system. A plain bronze bush where the prop enters the hull - a bronze stern tube - ending in a packing gland like yours. Either end just screws into bearings at either end. The whole thing is then machined through for the prop.

A greaser then fills the whole tube with grease ( there is not much space between the shaft and the tube )
T E Norris re-bushed my outer bearing 10 years ago. The inner is the original from 1970's. I have changed the packing once. I can motor ten hours without so much as a drip. I seldom operate the greaser. There is little to go wrong !

The greaser on mine is on the packing gland unit. My packing gland is fixed with a bracket - so both ends of the stern tube are fixed rigid. I do have an R&D flexi coupling at the gearbox connecton.

I think the water lubricated bearings are just that - they have grooves and seawater leaks through. They are a graphite type material rather than plain brone.

You can get a packing gland that has a grease nipple on it. That would make more sence. I think the water type just leaks water into the tube - and the packing stops it entering the vessel. On my type - the whole tube is filled with grease.

T E Norris are really good at this stuff - they are really helpful - and their website has many stern tube options illustrated to give you an idea of how things should be.

http://www.tnorrismarine.co.uk/product/stern-tubes/

Geoff

 

[johnwest]

Just remember when adjusting the packing pusher to use a vernier scale so it is square to the shaft.

j

 

[ghostlymoron]

I would have thought that you might get problems with overheating without water to cool the packed gland. But obviously your experience is first hand.

 

[KellysEye]

>Nothing wrong with your current gland except they are usually messy and leak.

It's not a leak a stern gland with packing should be tightened until there is a drip every couple of minutes to keep the bearing cool. The previous owner had bought a plastic bowl that would fit under the gland, attached a hose and fed it into a container in the bilge. As the packing wears the drips will increase so just tighten the compression.