?Stuffing box?

[Gordonmc]

The Hillyard I bought toward the end of last year has the shaft disappearing into a stuffing box (?) which is grease lubricated, but I don't have a scubie about maintenance. A .5mm pipe runs from the top of the box to a grease reservoir in a locker. This reservoir has a screw cap, onto which has been welded a 35mm nut. I gather turning the nut forces grease down the pipe into the box.

1. What sort of grease should be used. The stuff in there at the moment looks like bog-standard axle grease.

2. How often should I give it a turn? So far I have just screwed it down until I feel pressure... but there is no sign of grease being exuded from the box.

3. There is some weeping from the box, but limited to a few drips. Should I take the precaution of stripping it down to re-pack?

Any wisdom welcome. For info. the motor is a Thorneycroft T90 4-cyl 35h.p. driving an unidentified gearbox, possibly a Hurth.

 

[PuffTheMagicDragon]

A .5mm pipe would be hard put to pass oil, let alone grease! Perhaps you mean '5mm'. The Grease to use is plain marine grade grease (e.g. KEENOL, or similar). You are correct in turning until you feel resistance; you should not be aware of any grease exuding along the shaft, past the stuffing-box nut. At the first opportunity you have, undo this nut and withdraw some packing, at least the first two rings to see what you have. If it's the 'old' type of grease impregnated, square-section, rope (usually stinks to high heaven of rancid fat) be aware that this needs a regular supply of grease, otherwise the wear on the shaft progresses at an alarming rate. I would replace it with a more modern PTFE type. This does not really require much grease and is gentler on the shaft. You check the tightness every couple of hours to correct any slack but this depends largely on the way that you use the engine revs. Main thing to remember is to check tightness / slack before each trip and also at the end, when everything had had a chance to get back to normal temperatures. Do not press it too tightly. After about 10 to 15 minutes of running the stuffing box should be barely warm to the touch (back of the hand). Any hotter than this means that you have been over-enthusiastic with your tightening: slacken off.

Wally

 

[ccscott49]

You have the definative answer! One of the best explanations I have seen!

 

[johnmuir]

I was also told by marine engineer that you sould be able to turn tha shaft by hand. If not you have over tightened.

 

[ccscott49]

I'd like to see you turn my 2 1/2" shafts, with 36" props and y brackets by hand!

 

[Gordonmc]

Many thanks. You're right, I meant 5mm, not .5. Slippy fingers!
Your advice is reassuring and welcome.