Stuffing Box - Setup and adjustment questions

[GwalarnYacht]

I have just been repacking the stuffing box on my project boat and having some difficulties to get the water drip amount right.

Strangely the amount of water dripping seems to cease when I run the prop, but comes back a lot (to a drip every few seconds) after stopping it. If I tighten it to get the drip amount to about 1 drop per minute, the box seems to get too hot (can't touch it anymore).

Essentially I loosen a bit, too much water drips at standstill. I tighten a bit, stuffing box gets very hot. What am I missing here?

I have packed it with 5 rings GTO Graphite gland, does that seem overkill? Is less better?

At the same time, I have noted the small seacock on top of the stuffing box (see picture), which was not connected to anything so far. If I open the cap, water streams into the boat in quite large amounts. What is this for, how is it setup?

[Uncle Bob]

Originally Posted by GwalarnYacht

I have just been repacking the stuffing box on my project boat and having some difficulties to get the water drip amount right.

Strangely the amount of water dripping seems to cease when I run the prop, but comes back a lot (to a drip every few seconds) after stopping it. If I tighten it to get the drip amount to about 1 drop per minute, the box seems to get too hot (can't touch it anymore).

Essentially I loosen a bit, too much water drips at standstill. I tighten a bit, stuffing box gets very hot. What am I missing here?

I have packed it with 5 rings GTO Graphite gland, does that seem overkill? Is less better?

At the same time, I have noted the small seacock on top of the stuffing box (see picture), which was not connected to anything so far. If I open the cap, water streams into the boat in quite large amounts. What is this for, how is it setup?

Attachment 231774

Hi, could that be a grease cup?

[GwalarnYacht]

Originally Posted by Uncle Bob

Hi, could that be a grease cup?

I thought about this too. It hasn't got any grease nipple or thread inside to attach a nipple. There is only a thread on the outside for the cap, or eventually to connect a hose?

The seacock thread is about 1 inch. On the inside, it conical and reduces to a hole of about 4mm (where the water streams in).

[Uncle Bob]

Originally Posted by GwalarnYacht

I thought about this too. It hasn't got any grease nipple or thread inside to attach a nipple. There is only a thread on the outside for the cap, or eventually to connect a hose?

The seacock thread is about 1 inch. On the inside, it conical and reduces to a hole of about 4mm (where the water streams in).

Hi, if the cap has a good amount of thread on it they were filled with grease and screwed on, periodically screwing a few more turns to push more grease in, until it will screw no further then its a case of remove cap, rinse and repeat.

[Reefmagnet]

I have the exact same stuffing box on my boat. That fitting is a greasing connection. It's for pumping grease in behind the packing to help seal it. Because the stuffing box is rigid, the packing will always start to leak due to shaft vibration and movement around the packing. I've fitted a length of plastic tube with a stainless steel grease nipple at the other end above the waterline and pump grease in every so often to stop the drip from becoming excessive.

[GwalarnYacht]

Originally Posted by Reefmagnet

I have the exact same stuffing box on my boat. That fitting is a greasing connection. It's for pumping grease in behind the packing to help seal it. Because the stuffing box is rigid, the packing will always start to leak due to shaft vibration and movement around the packing. I've fitted a length of plastic tube with a stainless steel grease nipple at the other end above the waterline and pump grease in every so often to stop the drip from becoming excessive.

Great, that solves one mystery. So you use a grease gun to pump the grease into a plastic tube that is fitted to the thread? I guess a small hose connected to the fitting one side and to the grease gun on the other side would work too.

How much grease are you pumping in there?
How many rings of packing do you use?
Roughly how hot does your stuffing box get?

Many thanks.

[Reefmagnet]

Originally Posted by GwalarnYacht

Great, that solves one mystery. So you use a grease gun to pump the grease into a plastic tube that is fitted to the thread? I guess a small hose connected to the fitting one side and to the grease gun on the other side would work too.

How much grease are you pumping in there?
How many rings of packing do you use?
Roughly how hot does your stuffing box get?

Many thanks.

Yes, that outlet is a standard NPT (I think) fitting and the conical shape is to accept a tube with an olive seal with the corresponding female nut on top. Originally mine used a length of copper pipe connected to a full sized grease gun (which was probably a replacement for the original grease cup). Didn't like that idea so I went to my local hydraulic fittings shop and got an adapter to fit a grease nipple directly to the stern gland, but figured later the nipple might be prone to leaking so got some more fittings and some 300psi nylon tube that allowed me to extend it above the waterline while at the same time making it easier to get to for greasing. Simple, cheap and works very well now.





+ I use a mini grease gun and give it about half a dozen pumps
+ I've got three or four rings of 3/8" square packing (32mm shaft diameter)
+ I've measured with my point and shoot IR temp reader and about 40C in 25 ambient from memory. This is with it clamped just tight enough to stop the drips with the grease in place. It's a waste of time doing the clamping bolts up too tight because the shaft movement just seems to push the packing out of the way and promote leakage (I don't have much space between the gearbox flange and stern gland).



If you look closely, you can see how the tube is attached to the gland.

[sva3]

Is that a gate valve?

[Mark Thurlow]

NO,NO<NO. It is not a grease nipple or even a grease point. These stuffing boxes take Teflon coated braids that wear away over time.

The cap on top is a seawater flushing tube driven normally as part of the engine cooling raw water system. Many times these hoses are disconnected and capped like yours is. Reason given to me was to cut down on sea water fail points. The gland will work without the raw water if the correct lubricated braid is used.

I suspect you are having adjustment issues either because you have used the wrong sized braid or some old dry braid was left inside the coupling when you filled it up with new braid. Either way check the braid and make sure old stuff removed.

I notice that your port side stud is either screwed in too far or is too short to allow you to fit a second/lock nut as there is on the starboard side. I would fix this as well.

[sailor_ed]

Mark,
Sorry, it is a grease cup NOT a flushing tube fitting. You remove the cap, fill the cup with waterproof grease, replace the cap and screw it in a few threads every so often to grease the bearing. These used to be very common fittings on all sorts of equipment with rotating shafts.


The bolted housing looks roughly parallel to the packing so there is probably just some thing odd about the bolt lengths. Impossible to tell if the packing is correct but at this point there is nothing to say its not.


Ed

[adjo]

Graphite lubricated packing is slightly abrasive and eventually wears away at the shaft.
Teflon is better.

[Reefmagnet]

Originally Posted by sva3

Is that a gate valve?

Yes. And even worse, it never gets turned off because it"s the cockpit drain.

[mitiempo]

Originally Posted by adjo

Graphite lubricated packing is slightly abrasive and eventually wears away at the shaft.
Teflon is better.

Not sure about it being abrasive but it is a metal and more noble than stainless. Often causes shaft corrosion as the shaft becomes the anode.

ABYC specifically says not to use graphite shaft packing.

[RogerLloyd]

The shaft seal needs grease. The grease arrives under pressure via a tube which connects by the fitting you have observed. The other end of the tube is connected to a special grease gun. This "gun" is a cylindrical tube full of grease. The bottom end of the tube is screwed into a base plate which is screwed to the floor inside a cockpit locker. The other end of the cylinder has a "T"-handle. When the T-handle is turned clockwise grease is forced out of the cylinder and down the tube to the stern gland. The T-handle should be turned about half a turn every 4 hours or so when motoring, and also after the engine is switched off, in order to seal the tube while the boat is left to itself. When you have exhausted the grease in the cylinder, unscrew the cylinder from its base plate, and put that end into tin of e.g. Ramanol grease (this is suitable for under water and does not leave a residue, and hopefully is not too bad for the eco-system). The grease in the tin should have a top-plate which has a hole in it. Push the open end of the cylinder down onto this hole, and the grease enters the cyclinder through the hole in the top-plate. You will also have to pull the T-handle out to suck the grease in. When the cylinder is full, screw it to the base-plate again and turn the T-handle clockwise until resistance is met. See
http://www.asap-supplies.com/product...-150ml-2-74905

[Mark Thurlow]

Originally Posted by sailor_ed

Mark,
Sorry, it is a grease cup NOT a flushing tube fitting. You remove the cap, fill the cup with waterproof grease, replace the cap and screw it in a few threads every so often to grease the bearing. These used to be very common fittings on all sorts of equipment with rotating shafts.


The bolted housing looks roughly parallel to the packing so there is probably just some thing odd about the bolt lengths. Impossible to tell if the packing is correct but at this point there is nothing to say its not.


Ed

Really sorry Sailor_Ed but you are wrong, It is NOT a grease reservoir, as these are supplied to be used with pre lubricated (graphite/Teflon) braid. It has a cap not a grease screw on it. If you add grease where this cap is it will simply lodge on the water side of braid and not lubricate the braid, which is forward of the cap.

However this is the internet, not all advice is correct: let the OP decide. Fair winds.