Prop shaft seal?

N

Neil

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As an inboard neophyte, I'm slowly coming to grips with the engine. I'm working myself up to doing a service. However, while poking about to see what's what, I came across some sort of fitting on the prop shaft, with a tube coming from it. The tube leads to a knurled fitting which can rotate in each direction. I'm guessing the prop shaft end is for sealing and lubricating the prop shaft, the tube carrying some sort of lubricant, and the knurled knob some sort of lubricant applicator control.

What are the correct terms, function, modus operandi and service of these bits? Also the prop shaft bit is covered in green crud? do I need to be concerned?

I'll post some images when I find out how to delete files from my file upload manager, which is now full..............

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My greasy stern gland died last season, and by coincidence today I spent 5 hours contorted behind the engine in 1 cubic metre of space fitting a new one (water cooled/lubricated) from ASAP Supplies. Had to dismantle the gearbox/shaft coupling - which hadn't been done since the boat was new 30+years ago I reckon.
I enjoyed a deep, v hot bath tonight.
It LOOKS the business and I just hope that I don't sink when the boat goes back in the water next month..................
 
Neil said:
How do you get photo bucket links to show the pics? Did it!

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Good old fashioned stuffing box. The outer nut is to adjust pressure on the fibre sealing rings inside the housing and wrapped around the shaft. The tube is full of water and the seal is adjusted so that the shaft turns freely but not so tight that it runs hot, nor loose so that excess water drips out. The container holds grease and you turn the top from time to time to keep the seal lubricated. The rubber hose allows the shaft to move in relation to the stern tube and needs regular inspection to ensure it is sound.

Many people have replaced this type of seal with different designs that are not messy and do not drip water.
 
Thank you! Now I just need to find out how to get at it, and not just hold my phone at arm's length!

What sort of other designs might it be replaced with? I looked up other packing materials, but anything completely different?
 
Neil said:
Thank you! Now I just need to find out how to get at it, and not just hold my phone at arm's length!

What sort of other designs might it be replaced with? I looked up other packing materials, but anything completely different?
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Why change it, mine is 35 yrs old doesnt drip or spew grease out. from cold the shaft easily turns by hand so not over tight.
 
Neil said:
Looked at that site, bit no mention of the tube that comes out of mine. I don't know what the jubilee clip is for either.........
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Not all seals of this type have a grease feed and there is doubt as to whether they are of any value. A hangover from the days when there was often a white metal bearing inside the stuffing box which did need grease. If it does not leak then no pressing need to change it, although might be worth repacking and cleaning up.
 
Let's assume that the stern gear has seen little TLC since the boat was built - the healthy green patina suggests this may well be true! In the short term these things do go on working despite neglect or even lack of use, but if the boat is currently out of the water and you have the time it would be a good idea to totally refurbish it. Due to age, the flexible hose really should be replaced. It is a specialist type of hose, not just a bit of spare heater hose, as it has to hold the assembly against any torque transmitted through the bearing. You can get replacement hose either from a Chandler or direct from the rubber factors who make and supply such items, but make sure you have exact dimensions before buying. Ideally both ends of the hose should be double clipped but we all know that manufacturers don't make the spigots long enough to get two Jubilee clips on. Talking of that, make sure you get stainless Jubilees - as you already know, it's not going to e ewasy to get at them to change them if they rust.

The whole seal housing really wants to be cleaned out, wire brushed to get all the green deposits off. Green is normal where salt and moisture have been on the surface, but when cleaned there should be no pink areas - these occur when the zinc has corroded out of the metal, leaving only a loose matrix of copper, which is not up to the task. A bit of pink on the surface which can be rubbed off with emery doesn't matter, though. I always rub over the whole thing with a little grease to slow up future corrosion. measure the inside of the housing and the diameter of the shaft, subtract one from the other and divide by two to get the thickness of gland packing required. There's been some discussion about new materials for packing and there have been failures in some installations, so on the basis of it lasting this long the old material type should do the job. Wind the packing around the shaft and cut across at 45 degrees and stagger the joints when fitting.

Rob.

P.S. I suspect the third Jublee clip is being used to lock the compression nut, which may or may not be neccessary.
 
The boat won't be out of the water until I lift it for antifouling. I may have some time between coats to give it some attention. The boat's engine was replaced late 2012; I'm hoping they'd serviced the stuffing box at the same time, though the green patina might suggest otherwise.
 
Neil said:
Looked at that site, bit no mention of the tube that comes out of mine. I don't know what the jubilee clip is for either.........
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As Tranona said the tube is connected to the remote greaser. Screw the top off, fill with grease, tightening it pushes grease down the tube into the gland.
 
Actually, I remember the seller saying the prop shaft was replaced (it's a 20mm shaft, which wasn't the original (?) Sadler shaft size?), so they must have done something with the stuffing box?
 
Just heard back rom the previous owner; the gland was repacked when they put in the new engine (of course, why wouldn't they), so the green gunge is probably cosmetic....hopefully I won't have to think about it for a year or two
 
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