stuffing box

[Guest]

My Colvic Watson MS has a rigid shaft stuffing box that needs re-packing, but it is not arranged like the diagrams in Nigel calders book. Mine clearly requires the packing to go inside the large hexagon nut, not down inside the enlarged shaft tube with a compression spacer - it seems to me that mine is less secure simce less of the packing is in contact with the stern tube?? Any experiences out there? The shaft is 1.5" diameter, has a screw-down greaser (for the bearing) and the box bearing-casting has BRLCO or BRENCO cast into the top of it.


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[colvic]

Hi there,

First thing first; the name is BRENCO, but if you are like me you won't be able to find any new ones as they have long since ceased manufacturing.

On our Colvic MS we have 1" shaft with a stuffing box that sounds very much like yours, though I have fitted a remote greaser. I agree that it does look as though you would put stuffing inside the end fitting, but I did manage to buy some that was the correct thickness to go between shaft at outer tube. The end fitting then screws down and you lock that in place with the lock nut.

I don't know if the procedure is correct but I made sure there was plenty of grease inside the fitting, screwed the end cap down until the shaft was difficult o turn then slackened off a little, then ran the engine with the prop turning at about 700 rpm for about 1/2 hour, then shut down, waited a few minutes and checked to see if the end cap neded further tightening. Just a little tweak to stop the odd drip and screwed up the lock nut and 900 miles later all was still well.


Phil

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[Jools_of_Top_Cat]

The 'gutter' in the nut is there to pack down the packing without distorting it, at least that was my make on it. Insert your three or four strips at 45° and screw down the nut to a little over finger tight. Don't forget to grease up the strips prior to fitting.

After your first run you will need to re-adjust nut as it will have all bedded in, you should get the odd drip during running, and the shaft should feel fairly free, too tight and it will get hot.


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[Johnjo]

Also suggest the lock nut is good and tight as with the sound of
your arrangement it would be possible for the packing nut to either unscrew or tighten depending
on the rotation of the shaft.

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[PaulAG]

Also, has the stuffing box got a "flexible" but stiff rubber tube on it? If so, think about replacing it.
If there is a chance that the shaft could come loose from the gearbox coupling (and it could - happened to me twice in mid-Channel), make sure there are two well-tightened jubilee clips on the shaft between the gearbox and stuffing box. The exit hole for the shaft will let in more than a few drips!

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[colvic]

Does happen! Went back in the water after new engine etc. fitted and kept testing engine over the space of a few days, under load. Forgot all about the stuffing box until the auto bilge pump started cutting in every few minutes!

Phil

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[Guest]

Thanks for replies to all. I'm still confused about this stufffing nut. The exposed end of the shaft tube, once the nut is removed (and the shaft), is a solid bearing liner inside the stern tube - looks brass-like and has grease-grooves in it, inside the stern tube and is a snug fit over the 1.5" dia shaft. So there's no way the packing goes inside the stern tube part - it must go inside the nut. BUT, if it does, it seem to me that all of the sealing is being done by just the one end face of the aft piece of packing, pressing up against the end of the stern tube - if it leaks there, anything forard of it wont help. Or am I being thick? Anybody know where there's a drawing of how it is meant to be?? Mine's certainly not like the diagram in Nigel Calders book, and theres no rubber connecting-tube. Or am I worrying too much??!

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[DavidGrieves]

Hi
Have you really got a stuffing box type stern tube? I sounds to me like you have a "white metal" bearing. This arrangement as far as I know does not have any stuffing at all, it relies on the close fit of the bearing and grease pushed into the stern tube to keep the water out. White metal can be replaced by specialist enginering firms who will first "tin" the surfaces of the bearing, then pour molten whitemetal into the hole, then rebore it out to the requierd size. This wil only need to be done if excessive play is evident in the shaft. This type of bearing liner is also used on some large connecting rod bearings on older machinery insted of using shell bearings.

Hope this helps and doesn't confuse you more!!!

David

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[DavidGrieves]

Hi
Have you really got a stuffing box type stern tube? I sounds to me like you have a "white metal" bearing. This arrangement as far as I know does not have any stuffing at all, it relies on the close fit of the bearing and grease pushed into the stern tube to keep the water out. A friend of mine has this setup on his Hurley 22. White metal can be replaced by specialist enginering firms who will first "tin" the surfaces of the bearing, then pour molten whitemetal into the hole, then rebore it out to the requierd size. This wil only need to be done if excessive play is evident in the shaft. This type of bearing liner is also used on some large connecting rod bearings on older machinery insted of using shell bearings.

Hope this helps and doesn't confuse you more!!!

David

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[richardandtracy]

This type of bearing is also called a 'Babbitt' bearing.

I'd be surprised if the bearing is one of the Babbitt type, they went out of fashion 50-60 years ago. If you need to know a little about Babbitt bearings, take a look at http://www.lindsaybks.com/dgjp/djgbk/babbitt/index.html .

Regards

Richard


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[vyv_cox]

Cast Babbitt bearings are, as you say, old technology. However the material, something approximating to Tin 88% Antimony 5% and Copper 5% is the most widely used bearing material in machinery of every type except automotive. Nowadays it is used in far lower thicknesses with steel backing.

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[DavidGrieves]

Yeah they may be out of fashion, but I know of two boats in Whitehaven with this setup, one a Hurley 22 and a more modern Cobra 750, both have no stuffing box!!!

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