Repacking a Shaft Advise

[BrianW]

Folks,

I need to repack the shaft on my boat. It's not set up like a lot of the pictures I see on-line. Here's what it looks like...

http://img.photobucket.com/albums/v136/BrianW/PB050006.jpg

I'm fixing the bilge pump wiring for that area, so there will be less water when it's time to turn a wrench. I don't even know what size packing to buy. Right now the boat is in the water, and I really would like to do this while she's afloat. I'd have to check the tides to see if the grid is even an option. But, I never put a boat on the grid, and this is one big, heavy boat! Not sure which is a scarier proposition, given the number of boats I've seen keeled over on the grid in town.

I know I need to loosen the 6 nuts on the 3 studs and pull back the tube over the shaft, remove the old packing material, wrap the packing material over the driveshaft and cut to size, and reinsert. But, I'm looking for any and all advise on how it goes in the real world.

Thanks!

[sdowney717]

It looks like the tube studs allow a tightening adjustment on the packing. Do it the same as you would for a packing nut.
Taking out the old packing would tell you the size and number of rings needed. looks like it could be 5/16 or 3/8. I would say put enough rings in to allow for some adjustment later on. Those studs are really long and your collar is way down. Make sure you get all the old packing out. Are you doing this in the water? Make sure those studs are serviceable before trying to take it apart.

[TONYB]

Mate , forget that pre homo sapien style gland and fit a dripless seal like PSS, you won't have the mess and maintenance.
Tony

[ion barnes]

Brian, it appears to me that the follower, the part retained by the three studs is almost hard up against the body, which indicates that the packing has outlived its usefulness. You already know that because that why you are here.

If you want to repack while in the water, you need to raise the stern till the shaft is almost out of the water to limit the flow coming in while you are trying to push new packing in. I have heard of such sujestions as puting a dinghy on the foredeck and filling it with water to lift the stern. Has to be a sturdy dinghy so as to not open its seams!!

After that, you can back off the nuts and draw back the follower. Now you can tell what size packing you have by measuring the OD of the follower and the OD of the shaft and divide by 2. The number of turns of packing is determined by the length of the follower and could be 5-7 turns. You want to be able to just engaged the follower into the body and start the nuts. Do not attempt to tighten the packing beyond that point until you have the shaft back in the water and then only take up a little more. Final adjustments have to be made under way, keeping a close eye on the temperature of the housing and the amount of water dripping by. You need a little water always passing by and the housing should not get above warm after an hour of continuous running.

This is a ballpark description so far.

[cbob]

Brian, You didn't state how far below the waterline this packing gland might be, but on ships, packing of a known size was added prior to the next drydocking, with the aid of fingers keeping the existing packing from forcing itself inward from the water pressure (done at minimum draft aft where possible) before seals described above(in boats)etc. but for each foot below the waterline the water pressure is less than 1/2 psi per foot. The size packing required is the thickness of the gland holding the existing packing in place. If your looking for an experiential recommendation, lightren up,aft as possible, withdraw the gland, keeping the existing packing from forcing inward out of the gland somehow, assume you have 2 to 4 psi pushing it in, which should be no problem, add two or more rings, butts opposided somewhat, 2, 4, 6 oclock,etc. Flax packing can be thinned or fattened by hammering flat from whichever side, as necesaary. You should not need to haul out till next scheduled, and at that time, remove all, and install new as the size measured requires, butts stagered. I use the teflon impregnated type, which requires more attention than tallow, but lasts longer, to setting up and re setting. The double nuts are to hold the setting in place until the next readjustment. Fitting a dripless usually requires a haul out, coupling removal etc. for installation so you will then have time to choose, tried and true vs. modern dripless, if you can't stand drips and don't want to monitor this item, you might want to go for it, price and labor to instrall? Trade off. Hope this helps, cbob

[BrianW]

My best guesstimate is the packing gland is 4-5 feet below the water line. I can stand upright on the floor were the gland access hatch is located and not hit my head on the top of the hold. Here's a picture down into the hold (it's the aft hold) metal bin boards end right at the hatch, but it can't be seen in this picture...

http://www.imagestation.com/picture/sraid120/pc581f1e052b26f46a776d70e5032fc0f/f85eaa34.jpg

...here another idea of the depth, but in the forward hold, again the raised center section is the shaft alley running under the hold...

http://www.imagestation.com/picture/sraid120/p14ea0353f0406e063a68a98671108dc5/f85eaa68.jpg

This is the same boat I started the 'raising a wheelhouse' thread about...

http://www.imagestation.com/picture/sraid132/pec3ef1e80362641bf3da501591eb0a60/f79e7ca7.jpg

I'd really like to do this job in the water. There's not a lift in town which can haul her, and the grid still makes me nervous.

While I appreciate the input, I have no desire to switch to the dripless versions. The shaft is at least 3 inches in diameter, and those things are expensive! This system has worked for 63 years, I think it will work a bit longer. smile.gif

Tomorrow I plan on loosening up the three nuts (after backing off the locking nuts,) and see what happens. If the water starts rushing in right away, I'll need to reconsider the grid option. Frankly, I think it will, as it's already a steady trickle. As mentioned, the follower is darn near seated against the body. I don't think the previous owner ever repacked the thing.

There little chance of raising the stern. It's riding a bit high now, as the holds are empty and there's only 900 gallons of fuel in the stern tanks (they hold 2,000 full.) I can tranfer another 300 gallons or so to the daytank which is located nearer amidship.

The local marine supply store has been closed all week for inventory. They open tomorrow so I'll go see what kinds of packing material they have on hand. I'd prefer the teflon stuff, but the basic flax will still be a big improvement.

I did fix the wiring to the bilge pump for that area. It was broken at the float switch. So now I can get the water level down below the whole deal, but not by much. I have a 120v water pump, a Honda gas powered dewatering pump, plus several more bilge pumps located up forward in the engine room if things start to go bad.

What are the chances that I loosen the nuts most the way, then decide the water flow is too much, but in the process the remaining packings become dislodged by water pressure and I can't get the follower to reset the old packings?

Thanks for all the help so far!!! Really! This is a heck of a first maintenance problem to deal with right off. I'm a mechanic, but not a boat mechanic. So I've got the wrenching skills (20 years of fixing helicopters) but need some instruction to head in the right direction. You guys are providing that today.

[PeterSibley]

A suggestion, it may or may not be applicable.If you think that the water flow will be excessive could you closely fit a sheet of plastic around the outsie of the gland.It would be easier if the prop weren't fitted.Water pressure would tend to force it into the gap if a flow developed and at such low pressure even a supermarket bag would be strong enough.

[sdowney717]

I am using GFO packing
and it works great
Flax packing can score shafts

http://www.e-marine-inc.com/products/gfopacking/packing.html

Do some of your looking, I found out the CG and Navy are using this stuff.

[cbob]

Brian, Another thought, which is a common method for this application is the same idea as Peter's suggestion, but you will still need a diver. The ones we used were the hard hat professional type, not cheap. As well as the the plastic bag, try and find a local diver with experience doing this and ask how they have done it, and or hire him. I don't remember what they used, but they wraped the outer end of the stern tube with something, some non water soluable clay or sealant similar to the grey clay looking stuff the sell in auto supply stores for sealant (dum dum) between body parts, older vehicles, or rags or soft rope. As you withdraw the gland slowly, an increase in ingress should indicate if the existing packing is pushing inwards. if it is jammed in as it looks like, it probably won't come apart, as you suggest.
When you finally haul and do this right, pay close attention to the shaft surface in way of the packing area watching for necking or pitting wear. If this turns out to be the case, packing will wear more rapidly.
BTW I have a stainless shaft installed in 79, Used teflon and flax since then, renewed every five to eight years, the shaft has no wear whatsoever. Wear to the shaft results from failing to adjust properly, to allways maintain a slight (drip) water flow for cooling. After repacking, the gland will warm up, expand and stop the water flow, then heat up a lot and burn the packing, so you want to insure that setting up on the gland with new packing doesn't stop the drip, for the first few hours of run in. Luck again, cbob

[John Meachen]

I have no experience of trying to repack a gland of this size with the boat afloat.Having said that,I would be inclined to try to obtain at least one and preferably several auxiliary pumps.I would also seek a small blowlamp and a tapping drill for the studs together with a length of studding or a full set of replacement bolts.Packing and grease go without saying but refill the greaser before starting the job.Basically,prepare for everything that can go wrong and then when it does you should be alright.If evrything goes without a hitch you will have a selection of useful spares for next time.Salty looking boat by the way.

[BrianW]

Okay folks, here's the update.

I talked to the guy who owned the boat before the guy I bought it from, and he had repacked the shaft before. While he didn't remember the correct packing size, he told me that doing the job while in the water would be no big deal.

So I started by rounding up some tools (good advise from above) and all the various packing material that was on the boat. Unfortunately, there were several different sizes onboard, so that part didn't help much. Then I went ahead and removed the jam nuts. Sure enough, one of the studs started backing out, rather than the nuts coming off. I decided to just go ahead and remove the whole stud, while 'feeling' for any signs of stripped out threads. It came right out, and the threads were fine. Turns out the adjustment nut had been run up tight on the stud where it goes from threaded to non-threaded. I threw the stud in a vise, put on two jam nuts tightened together, and broke the torque on the trouble nut. After that, the stud and nuts were fine. So using the two jam nuts, I globbed a bunch of locktite on the stud and reinstalled it.

Then I started loosening the other two nuts and worked the collar out of the housing. It was a pleasant suprise that water didn't start pouring out, and it just continued to trickle. I grab up the flax I had on hand, and found the size that seemed to fit best. Turns out it was 1/2 inch, although I was tempted to try and force some 5/8th's flax into the opening. It just wouldn't fit, and I figured it would be too tight anyhow. The half inch stuff fit snug and I was able to push it in with my fingers. Naturally I only had enough of the 1/2 inch flax for one wrap, so I ran to the parts store and bought some more. They didn't have any fancy packing material, just plain ol'flux (if that's the correct term?) I stuffed three more wraps into the gland, for a total of four.

Here's what it looks like now...

http://img.photobucket.com/albums/v136/BrianW/PB070001.jpg
http://img.photobucket.com/albums/v136/BrianW/PB070005.jpg

I tightened it up 'snug' and as evenly as possible, judging by the gap around the shaft. There's still a steady drip though. That area of the bilge keeps filling up a bit too fast, but I'm not convinced it's all coming from the stuffing box. I will check things out farther aft tomorrow. Perhaps a rudder packing? It's no big deal, as it seems to on;y fill up so far, then stop. The bilge pump rarely has to run. Just would be nice if it were dryer.

I've got to add some coolant to the main (perhaps another topic) before I can turn the shaft. It would be nice to do it right at the dock, but there's this sail boat...

http://img.photobucket.com/albums/v136/BrianW/PB070006.jpg

...right behind me, and I doubt he'd appreciate all the prop wash. smile.gif Is it okay to run it in reverse the first time?

Hindsight being 20/20, I may have installed one too many wraps. I guess I'll know for sure when I finally get underway. smile.gif

Thanks for all the help! I'll do a better job next time she's high and dry.

[John B]

Hi Brian,Did you coil it around or did you cut them to make "discs" with staggered butts ?

[BrianW]

I cut them. The first one I put the butted up ends at 12:00 the second at 9:00, the third at 3:00, and the fourth again at 12:00 o'clock. I know the last should have gone at 6 o'clock, but I wanted any last seep located at the top of the shaft so I could see it easier. Not sure that worked though, as I thought I could hear it dripping at the bottom. Plus their were small ripples in the water already in the bilge there. But, I need to go back with an inspection mirror tomorrow and get a better look.

Someone else had used the term 'wraps' and I just stuck with it. Sorry for the confusion.

[cbob]

Brian, If my memory serves, we used to have one nut on the outside and one on the inside of the "collar flange" rather than both on the the out side as you show, like jam nuts. This allows for controlled withdrawal. Otherwise I think you've got it. I'm going to check out that emarine packing idea myself, looks interesting. cbob

[ion barnes]

In regards to the coils or wraps, the old school of thought was that the rotation of the shaft could cause a coil of packing to tighten up or constrict onto the shaft and spin in the housing. In practise, I disagree in that the follower is compressing the packing lengthwise in the houseing and since it has no where to go, it pushes against the housing wall, cant go there, so it bears against the shaft.

I have had to replace packing in some rather awkward spaces and getting it all out is really difficult at times. Anything left in will cause the new packing to not properly seat. So, I use a continuous coil with the hope that if I am the next guy to re-pack, I can pick out the end and yard out the entire piece rather than one piece then another, not being too sure I got it all.

As for the material of choice, I vote for teflon/graphite rope. Easy to work with, and wont score a shaft even if overtightened.

[BrianW]

cbob,

Having a nut on each side is a good idea! I did have to pry a bit to get the collar to come out, even when the nuts were completely backed off. So much for my fears of the ocean rushing in. smile.gif

Having the nuts on both side would make it easier to get off, but it would limit some travel as the stuff wears out and a person just wants to tighten things down a bit more.

I went back today with a mirror, and it was a steady trickle coming from the stuffing box. So I tightened up some more and got it down to a drip a minute. That may be too tight, but I wanted to make sure it could be done. I'll loosen them when I get the shaft tutning.

I've got a $75 gift certificate from Waste Marine. Think I'll order up some of the better packing material for the next time around.