Stern Glands.
The traditional method for keeping the propeller shaft watertight is the packed gland or stuffing box, with rings of a soft packing material are placed around the shaft inside the gland nut.
Three or four rings are normal for narrowboats.
For those of you not sure what this is, its the brass tube that the propeller shaft passes through to exit the boat and always seems to leak into your bilge.
It usually has a pipe from it leading to the stern gland greaser/lubricator
Three or four rings are normal for narrowboats.
For those of you not sure what this is, its the brass tube that the propeller shaft passes through to exit the boat and always seems to leak into your bilge.
It usually has a pipe from it leading to the stern gland greaser/lubricator
Various materials are used for the packing, traditionally flax, hemp and cotton, but more modern materials include graphite, acrylonitrile and Kevlar. Packing materials may be impregnated with grease or PTFE lubricants. Packing is normally square in section and comes in a variety of dimensions.
The gland should give a drip every minute of two when under way, but not leak when stationary.
Here are the two main issues, too loose and it leaks, too tight and it wears the prop-shaft.
If you put your boat back into the water and your gland is too tight the cutlass bearing will overheat and burn out, The bearing is lubricated and cooled by water and it cant get in because its air locked by the packing, my tip is to loosen the gland till you get some water, then nip back up.
The only real 'DIY' repair possible is to nip up the two bolts to slow a leak, saying that for the more adventurous re-packing the stern gland is not a major issue.
Here are the two main issues, too loose and it leaks, too tight and it wears the prop-shaft.
If you put your boat back into the water and your gland is too tight the cutlass bearing will overheat and burn out, The bearing is lubricated and cooled by water and it cant get in because its air locked by the packing, my tip is to loosen the gland till you get some water, then nip back up.
The only real 'DIY' repair possible is to nip up the two bolts to slow a leak, saying that for the more adventurous re-packing the stern gland is not a major issue.
Re-packing a stern gland
Firstly If you are concerned about the amount of water that may leak in on a narrowboat you can remove the weed hatch and wrap cling-film or mastic bandage into the space between propeller and back of boat.
Remember to remove it before putting the boat in gear
Having decided that it is now time to re-pack the stern gland you must first of all consider how much wear you have found. The greater the visible wear the more worn the bearing surfaces are likely to be and thus the greater volume of water is likely to leak in when the packing has been removed.
If the gland has a remote greaser as most canal boats do, tightening this down may well stop almost all leaking.
Next you need to find out what size and type of packing is required. The packing comes in white and black varieties. I use the black as it contains the natural lubricant, graphite which does not react with freshwater.
The packing is usually to be one of three sizes 6mm (1/4"), 8mm (5/16"), or 10mm (3/8"). If your boat manual does not give this information you need to measure it.
Remember to remove it before putting the boat in gear
Having decided that it is now time to re-pack the stern gland you must first of all consider how much wear you have found. The greater the visible wear the more worn the bearing surfaces are likely to be and thus the greater volume of water is likely to leak in when the packing has been removed.
If the gland has a remote greaser as most canal boats do, tightening this down may well stop almost all leaking.
Next you need to find out what size and type of packing is required. The packing comes in white and black varieties. I use the black as it contains the natural lubricant, graphite which does not react with freshwater.
The packing is usually to be one of three sizes 6mm (1/4"), 8mm (5/16"), or 10mm (3/8"). If your boat manual does not give this information you need to measure it.
Remove the nut(s) and any pusher and measure the gap between the shaft and outer sleeve. Replace it all and tighten the gland to stop any leaks.
Write the size required in your log or boat manual ( as recommended in the Hands on DIY Page) and then purchase the appropriate packing.
The first thing to do is cut the packing material into rings, making sure your knife is very sharp otherwise you may fray the end of the packing which can cause the gland to leak more than it should.Start by wraping ithe packing around the main shaft, and using a very sharp knife cut at right angles to the packing to form a ring with a but joint.
The other option is to cut at about 45 degrees to the packing to form a scarf joint, both ways seem to work OK so don't worry which one you use.
Write the size required in your log or boat manual ( as recommended in the Hands on DIY Page) and then purchase the appropriate packing.
The first thing to do is cut the packing material into rings, making sure your knife is very sharp otherwise you may fray the end of the packing which can cause the gland to leak more than it should.Start by wraping ithe packing around the main shaft, and using a very sharp knife cut at right angles to the packing to form a ring with a but joint.
The other option is to cut at about 45 degrees to the packing to form a scarf joint, both ways seem to work OK so don't worry which one you use.
Now its time to remove the old packing, although some people simply add more packing on top of what is already there.
This may be fine in an emergency, but the old packing will have lost a lot of its "body" and is likely to be hard and worn. It is best to repack from scratch, so you need to get all the old packing out.
Now many people will say you need a special removing tool, for me I use the longest wood screw I can find with a Phillips head and screw it into the packing material.
Remove the nuts and any "pusher" and screw the screw into the old packing , then use pliers on the screw head to pull the screw and old packing out. Repeat until you can feel the screw scraping on bare metal.
At this point the water may be jetting in, but it will be at low volume. This is where you will be grateful that you prepared the packing before taking the old stuff out! You have lots of time so don't panic.
This may be fine in an emergency, but the old packing will have lost a lot of its "body" and is likely to be hard and worn. It is best to repack from scratch, so you need to get all the old packing out.
Now many people will say you need a special removing tool, for me I use the longest wood screw I can find with a Phillips head and screw it into the packing material.
Remove the nuts and any "pusher" and screw the screw into the old packing , then use pliers on the screw head to pull the screw and old packing out. Repeat until you can feel the screw scraping on bare metal.
At this point the water may be jetting in, but it will be at low volume. This is where you will be grateful that you prepared the packing before taking the old stuff out! You have lots of time so don't panic.
Re-packing is simple, take a ring of the cut packing and push it down the hole using a blunt instrument and Note the position of the cut/join.
Push the next length in with the cut about 120 degrees offset from the first one, and repeat for the next length and so on.
Do not totally fill or overfill the void, leave at least 3mm of space above the top packing ring.
By now the leak should now have virtually stopped.
Push the next length in with the cut about 120 degrees offset from the first one, and repeat for the next length and so on.
Do not totally fill or overfill the void, leave at least 3mm of space above the top packing ring.
By now the leak should now have virtually stopped.
If the gland is still leaking gradually tighten the nut(s), turning the shaft with your hand* until the drip either just stops or drips once or twice a minute.
Now you can pump out the bilge and double check that all locknuts are in place and tight.
Run the engine in ahead and astern for half an hour or so. keep checking for leaks and adjusting (with engine stopped) as required.
Now you can pump out the bilge and double check that all locknuts are in place and tight.
Run the engine in ahead and astern for half an hour or so. keep checking for leaks and adjusting (with engine stopped) as required.
Water Lubricated
Water lubrication consists of a rubber ring, with a lipped profile supported by a spring, contained in a housing.
The rubber lip seal runs on the shaft to form the seal, This seal is generally used on Light duty, low pressure sealing, where low cost is required. It requires little attention other than ensuring that a water supply is maintained during operation.
It only requires a very small amount of special grease applying via the grease nipple every 300 hours.
There is generally no back up for the seal in case of failure. there is no requirement for an additional "back-up" seal.
The seal needs replacing at shorter intervals than the other seals to be safe and, prevent a "drippy" stern gear.
