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-   -   Shaft seal (http://www.sailnet.com/forums/gear-maintenance/25680-shaft-seal.html)

Edo Kazumichi 11-22-2006 08:56 AM

Shaft seal
 
I've got a bronze shaft seal. It was leaking so I put in some grease. Now it leaks about 1 drop ever 2 or 3 seconds when the engine is in gear but none at all when the engine is shut down. I know these things are meant to leak a bit but is this rate normal? Also, grease the color of dirty-cream has extruded from the front of the seal. Does this just mean that I put in too much?

Can somebody give me an idea of what's normal for this thing?

cardiacpaul 11-22-2006 09:14 AM

short answer.... it shouldn't be leaking at all, get it fixed, fast. It will get worse. A "dampness" is ok, but a drop is a drop, not good. (after typing this, I'm not sure this is making any sense at all, work with me, ok?)

longish answer.., the dirty cream color is the water emulsifying with the grease.
The reason why it doesn't leak "at rest" is there isn't enough water pressure to move past (displace) the grease when the shaft isn't turning.

FrankLanger 11-22-2006 02:18 PM

CardiacPaul,
I'm just trying to understand and continue to learn: how is this bronze seal different from a stuffing box which is supposed to drip a bit to lubricate the prop shaft? And if it's not supposed to leak any water, what lubricates the bronze seal/prop shaft when it's rotating? I vaguely remember that some bronze bushings are self-lubricating--is that the answer to my first question?
Thanks for any information.
Frank.

cardiacpaul 11-22-2006 03:46 PM

the stuffing box is lubed-sealed with either water, flax, some type of new fancy-schmanchy (technical term) no stick-um packing that keeps it turning and the dry in, and the wet out. . There really should be no water ingress into the boat. period.

good links...
http://www.e-marine-inc.com/products...g/packing.html
http://www.gore.com/en_xx/products/s...king_fiber.htm
http://www.boatus.com/boattech/Casey/StuffingBox.htm
http://www.docksidereports.com/stuffing_boxes.htm
http://www.alohaowners.com/pages/pro...uffing_box.htm
http://www.shaftseal.com/pss-shaft-s...struction.html

Some bronze bushing so do have a carbon/petroleum based lube imbedded in the bushing itself, but, this is not a sealing device, its a lube.

The cutlass bearing is a whole 'nother breed o'cat.
heres a really good link....
www.keeldragger.com/Projects/CutlassBearing.aspx

camaraderie 11-22-2006 03:56 PM

"A bronze shaft seal" sounds like a stuffing box to me. Edo...are you sure what you are describing is a shaft seal and not a stuffing box?
If it is a stuffing box then a drip or two a minute while underway is exactly how it should be performing.

k1vsk 11-22-2006 04:03 PM

Kind of difficult to respond after you already received a number of conflicting answers...
First, I'd suggest you check out the types of shaft seals there are as the type you have will dictate how tou should maintain it. The previous answers all seems to imply you have a certain type which is difficult to know without a further description. There are a number of how-to boat maintenance books available should you want to study up.
Of the various seals, some are supposed to leak, albeit slowly, and others are so-called dripless (and there are a few different types of these as well). Again, what you should do depends on what type you have. The good news is that it is apparenly leaking slowly so no worries as they seldom fail catastrophically.
Let's assume you have the older type grease filled seal and you have used the correct grease which is not water soluable. It should not leak at rest but may when turning. If this is the case, you're fine - if it is leaking at rest, there are two likely possibilities:
1. wrong grease, and
2. air pocket entrained in the grease container.

If you can be a little more specific about what you have and what grease you used, maybe we can eliminate the guessing of what might be a problem.
Don

FrankLanger 11-22-2006 04:39 PM

CardiacPaul, thanks for the great links--they answer just about any question one could have about stuffing boxes, seals, etc. :D
Frank.

Edo Kazumichi 11-23-2006 08:38 AM

Thanks for the input, folks, even if it is conflicting.

What do I have? Well, I don't know the brand but it's about four inches long, bronze and has a grease tit. There's no way to open it up to pack in anything. How would I go about finding the brand and thus the operational specs on it - i.e. if it should drip, when and how much?

cardiacpaul 11-23-2006 09:43 AM

if you've got a digital camera, a picture would help.

sailingdog 11-23-2006 11:03 AM

Don't forget to put something in the photo, like a ruler, to give a sense of scale...


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