Stern Gland - Packing

[henhullpilgrim]

I've just replaced the packing in my stern gland and am wondering if it's possible to 'overpack' it. Having replaced the previous three rings of packing with three new rings, the propellor shaft turns by hand (she's out of the water) but only if I turn it using the prop to get some leverage. I can't turn it by twisting the shaft alone in the engine compartment (although grease on the shaft doesn't help).

 

I've never had the need to spin the prop around before (unless removing stuff through the weed-hatch) and so have little experience of knowing how readily a prop should 'spin'.

 

The guy next to me can spin his prop around very readily (almost like a spinning plate) although he admits that he's never re-packed the gland in a number of years. Seems almost as though there's zero resistance in his set up.

 

Is this normal for there to be some resistance initially and that will things settle down once the engine gets going and the packing 'beds-in'?

 

I believe that I've used the correct size (8mm) packing. It went into the packing space (and looked very much like the old stuff for size) but did need some persuasion from the packing plate for each ring. Perhaps I needed the 6.7mm packing - does that small diference really matter? The rings were cut carefully too (at 45 degree angles) and I don't believe they're too long and certainly don't overlap.

 

Perhaps I've over tightened the packing plate? Who knows.

 

Any thoughts out there?

 

Brent

[by'eck]

I've just replaced the packing in my stern gland and am wondering if it's possible to 'overpack' it. Having replaced the previous three rings of packing with three new rings, the propellor shaft turns by hand (she's out of the water) but only if I turn it using the prop to get some leverage. I can't turn it by twisting the shaft alone in the engine compartment (although grease on the shaft doesn't help).

 

I've never had the need to spin the prop around before (unless removing stuff through the weed-hatch) and so have little experience of knowing how readily a prop should 'spin'.

 

The guy next to me can spin his prop around very readily (almost like a spinning plate) although he admits that he's never re-packed the gland in a number of years. Seems almost as though there's zero resistance in his set up.

 

Is this normal for there to be some resistance initially and that will things settle down once the engine gets going and the packing 'beds-in'?

 

I believe that I've used the correct size (8mm) packing. It went into the packing space (and looked very much like the old stuff for size) but did need some persuasion from the packing plate for each ring. Perhaps I needed the 6.7mm packing - does that small diference really matter? The rings were cut carefully too (at 45 degree angles) and I don't believe they're too long and certainly don't overlap.

 

Perhaps I've over tightened the packing plate? Who knows.

 

Any thoughts out there?

 

Brent

 

As long as the shaft turned freely with the packing removed I wouldn't worry too much. It will bed in & free up with use as you suggest. If necessary you could back off the gland a tad as long as it doesn't drip more than once a minute after a run when back in the water.

 

I would be more worried of your friends loose running shaft.

[bizzard]

I've just replaced the packing in my stern gland and am wondering if it's possible to 'overpack' it. Having replaced the previous three rings of packing with three new rings, the propellor shaft turns by hand (she's out of the water) but only if I turn it using the prop to get some leverage. I can't turn it by twisting the shaft alone in the engine compartment (although grease on the shaft doesn't help).

 

I've never had the need to spin the prop around before (unless removing stuff through the weed-hatch) and so have little experience of knowing how readily a prop should 'spin'.

 

The guy next to me can spin his prop around very readily (almost like a spinning plate) although he admits that he's never re-packed the gland in a number of years. Seems almost as though there's zero resistance in his set up.

 

Is this normal for there to be some resistance initially and that will things settle down once the engine gets going and the packing 'beds-in'?

 

I believe that I've used the correct size (8mm) packing. It went into the packing space (and looked very much like the old stuff for size) but did need some persuasion from the packing plate for each ring. Perhaps I needed the 6.7mm packing - does that small diference really matter? The rings were cut carefully too (at 45 degree angles) and I don't believe they're too long and certainly don't overlap.

 

Perhaps I've over tightened the packing plate? Who knows.

 

Any thoughts out there?

 

Brent

If your shaft size is 1.1/2''then 5/16 or 8mm is the most usual size packing for that size. You may have some other unknown resistance in the drive-line like engine alignment way out or a gearbox that is stiff in neutral for example.

You could uncouple the prop-shaft from the gearbox to satisfy yourself on those points if you wish.

but i'd back off those gland pusher nuts a bit ''equally'' and try to turn the shaft. Other than that i'd wait until the boats back in the water.The shaft and bearing will then also be receiving the added lubrication of water. You will need to readjust the gland a few times anyway between boat trips, until the new packing settles down and beds in.

[Barry]

 

Is this normal for there to be some resistance initially and that will things settle down once the engine gets going and the packing 'beds-in'? I think you are right

 

I believe that I've used the correct size (8mm) packing. It went into the packing space (and looked very much like the old stuff for size) but did need some persuasion from the packing plate for each ring. Perhaps I needed the 6.7mm packing - does that small diference really matter? The rings were cut carefully too (at 45 degree angles) and I don't believe they're too long and certainly don't overlap. Sounds fine to me

 

Perhaps I've over tightened the packing plate? Who knows. I doubt it

 

Any thoughts out there?

 

Brent

 

It sounds good to me

 

There will be a little resistance until the packing beds in but you can turn the shaft with a little extra leverage so thats good

 

If you are worried after a few hours running go down the weed hatch and see what the difference is - then try again a few running hours later

[henhullpilgrim]

Thanks for that guys. Puts my mind at rest. I'll see how it beds in when I return to the water.

 

Cheers.

[RobinJ]

I've just replaced the packing in my stern gland and am wondering if it's possible to 'overpack' it. Having replaced the previous three rings of packing with three new rings, the propellor shaft turns by hand (she's out of the water) but only if I turn it using the prop to get some leverage. I can't turn it by twisting the shaft alone in the engine compartment (although grease on the shaft doesn't help).

If this is the standard two bolt brass flange and provided you have the right size packing, you should put enough opacking in so the flange fits snuggly into the stern gland housing, many take 6 or 7 rings!

Yo need to make sure there is grease in the new packing and then tighten it up hard so the shaft does not rotate, then back off the nuts about 1/4 to 1/2 a turn each until the shaft turns fairly easily.

[bizzard]

I would not tighten those gland nuts up hard. If the tube bearing has wear in it ''sideways play'',packing material can be forced into the bearing and jamb it,and shaft will need uncoupling and manipulating to extract it.

[larkshall]

I would not tighten those gland nuts up hard. If the tube bearing has wear in it ''sideways play'',packing material can be forced into the bearing and jamb it,and shaft will need uncoupling and manipulating to extract it.

 

Been there done that one was a right sod of a job

[bizzard]

Been there done that one was a right sod of a job

Indeed a month ago a chap did this,didn't know he'd done it, started up put it into gear.The boat struggled along for an hour or two and then stripped the drive plate splines,i freed the shaft renewed the drive plate and then discovered the gearbox had been badly damaged too,a PRM 160 and i had to replace that also.

[RobinJ]

I would not tighten those gland nuts up hard. If the tube bearing has wear in it ''sideways play'',packing material can be forced into the bearing and jamb it,and shaft will need uncoupling and manipulating to extract it.

With new packing there should not be a problem in seating the packing by tightening up initially, as the shaft shiuld not be turned with it tightened. Plus the packing should seat sideways onto the shaft if inserted properly and not be forced back into the bearing!

[swift1894]

If this is the standard two bolt brass flange and provided you have the right size packing, you should put enough opacking in so the flange fits snuggly into the stern gland housing, many take 6 or 7 rings!

Yo need to make sure there is grease in the new packing and then tighten it up hard so the shaft does not rotate, then back off the nuts about 1/4 to 1/2 a turn each until the shaft turns fairly easily.

Dammit I think my stern gland may indeed need 6 or 7 rings. I put 3 in as per standard procedure although I must admit I seemed to take out more than this. Now I'm getting a lot of grease squeezing out of the gap between the gland housing and the outer edge of the collar rather than the gap between the shaft and inner edge of the collar. Trouble is I don't want to have to dry dock again just to do it.

Dare I risk taking off the collar and putting in another 3 or 4 rings, 1 ring at a time, or could the water pressure push the 3 new rings out with a deluge of water and dire consequences

[RLWP]

Dammit I think my stern gland may indeed need 6 or 7 rings. I put 3 in as per standard procedure although I must admit I seemed to take out more than this. Now I'm getting a lot of grease squeezing out of the gap between the gland housing and the outer edge of the collar rather than the gap between the shaft and inner edge of the collar. Trouble is I don't want to have to dry dock again just to do it.

Dare I risk taking off the collar and putting in another 3 or 4 rings, 1 ring at a time, or could the water pressure push the 3 new rings out with a deluge of water and dire consequences

 

It is normal to remove and replace all the packing without dry-docking. If you are worried, apparently wrapping a plastic bag around the prop shaft and end of the shaft bearing works

 

Richard

[alan_fincher]

In most modern stern glands I have seen I would say you would normally struggle to get anything like 6 or 7 full rings of the correct sized packing.

 

Generally in my experience if you start with no packing in there at all, they are full(-ish) by about 4 rings, although I admit there may be types I'm not familiar with.

 

Are you sure you are using the correct sized backing for your particular stern gear, because from the symptoms you describe it sounds like you might be using some that is too small.

 

The correct packing will be a fairly snug push fit in the gap - if it isn't, themn the chances are you needed a larger size.

 

As Richard says, you can usually take the whole lot out, sometimes with no water ingress at all, provided you have put lots of turns on the greaser before you start.

[Bod]

It is normal to remove and replace all the packing without dry-docking. If you are worried, apparently wrapping a plastic bag around the prop shaft and end of the shaft bearing works

 

Richard

I belive the plastic bag should be, behind the prop in the water, the idea being that water pressure against the bag, slows any leakage into the boat.

 

Bod

[RLWP]

I belive the plastic bag should be, behind the prop in the water, the idea being that water pressure against the bag, slows any leakage into the boat.

 

Bod

 

If you can wrap the bag around the shaft and bearing on the inside, and still replace the packing, you're a better man than I am. Yes, it goes around the shaft under the water

 

Richard

[swift1894]

It is normal to remove and replace all the packing without dry-docking. If you are worried, apparently wrapping a plastic bag around the prop shaft and end of the shaft bearing works

 

Richard

 

Good I'll give it a go then.

Thanks

 

In most modern stern glands I have seen I would say you would normally struggle to get anything like 6 or 7 full rings of the correct sized packing.

 

Generally in my experience if you start with no packing in there at all, they are full(-ish) by about 4 rings, although I admit there may be types I'm not familiar with.

 

Are you sure you are using the correct sized backing for your particular stern gear, because from the symptoms you describe it sounds like you might be using some that is too small.

 

The correct packing will be a fairly snug push fit in the gap - if it isn't, themn the chances are you needed a larger size.

 

As Richard says, you can usually take the whole lot out, sometimes with no water ingress at all, provided you have put lots of turns on the greaser before you start.

It's an old boat though so not a modern gland. The size I used is correct, it was a tight fit getting it into the gland.

 

I belive the plastic bag should be, behind the prop in the water, the idea being that water pressure against the bag, slows any leakage into the boat.

 

Bod

Thanks for the plastic bag advice. I see the logic of the water pressing on it to cut down on the ingress.

 

I guess the idea is to have as many rings as necessary to completely fill the void. I've just read so often that you put 3 rings in with the joints being 120 degrees spaced in the opposite direction to the rotation of the shaft in forward. Never thought to add more!

Edited November 8, 2012 by swift1894