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Old 10-02-2019, 18:10   #1
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Stuffing Box

I'm trying to figure out what type of stuffing box I have on my boat for the prop shaft.

See below picture of the stuffing box. Is it a dripless or a traditional stuffing box? I ran it for a few minutes in gear and didn't see any water dripping so if it's a standard one it may be too tight.

Thanks.
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Old 10-02-2019, 18:23   #2
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Re: Stuffing Box

Looks dripless. no nuts to tighten or loosen as found on conventional.
https://www.shaftseal.com/
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Old 10-02-2019, 18:27   #3
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Re: Stuffing Box

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Originally Posted by Calif.Ted View Post
Looks dripless. no nuts to tighten or loosen as found on conventional.
https://www.shaftseal.com/
Thanks for the quick reply. I was wondering because it doesn't have one of those tubes sticking out the side. The whole silver metal piece rotates against the black section when running.
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Old 10-02-2019, 18:36   #4
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Re: Stuffing Box

Later models have a method to "burp" air trapped in the bellows not found on earlier models. I've only sailed OP's boats with dripless so don't know for sure but seems odd if it rubs against the bellows.
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Old 10-02-2019, 18:41   #5
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Re: Stuffing Box

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Originally Posted by Calif.Ted View Post
Later models have a method to "burp" air trapped in the bellows not found on earlier models. I've only sailed OP's boats with dripless so don't know for sure but seems odd if it rubs against the bellows.
I believe the black piece where the silver cylinder rotates is not actuallly the bellows it seems like it is a piece of graphite or something hard. I was concerned if it was not a dripless because I thought maybe it cooked the rubber.
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Old 10-02-2019, 18:48   #6
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Re: Stuffing Box

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Originally Posted by felizcortez View Post
I believe the black piece where the silver cylinder rotates is not actuallly the bellows it seems like it is a piece of graphite or something hard. I was concerned if it was not a dripless because I thought maybe it cooked the rubber.
You got it right!

It is a hard carbon face seal. Dripless seals come in two flavors, a rubber lip seal, and what is usually called a "mechanical seal" where a hard carbon face rubs on a polished metal rim.

When you haul the boat, and the "water" side drains and fills with air it is important to retract the carbon face to let the water refill before running the engine.

These are reliable seals and will serve you well. The only danger is if a mechanical shock cracks the carbon face, with is rather brittle. Then leakage is fast and furious with no easy fix. until the boat is out of the water.
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Old 10-02-2019, 19:23   #7
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Re: Stuffing Box

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You got it right!

It is a hard carbon face seal. Dripless seals come in two flavors, a rubber lip seal, and what is usually called a "mechanical seal" where a hard carbon face rubs on a polished metal rim.

When you haul the boat, and the "water" side drains and fills with air it is important to retract the carbon face to let the water refill before running the engine.

These are reliable seals and will serve you well. The only danger is if a mechanical shock cracks the carbon face, with is rather brittle. Then leakage is fast and furious with no easy fix. until the boat is out of the water.

I'm assuming just a quick burp shoudl be sufficient? When I pushed it back today, I got sprayed in the face water came out so fast.
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Old 10-02-2019, 21:50   #8
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Re: Stuffing Box

Quick burp is fine as long as you get water coming out. The other risk with them is the bellows getting old and cracking. Some prudent folks renew it every few years.
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Old 11-02-2019, 02:14   #9
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Re: Stuffing Box

Quote:
The only danger is if a mechanical shock cracks the carbon face, with is rather brittle. Then leakage is fast and furious with no easy fix. until the boat is out of the water.
While I am a convert to dripless seals, and have now used one for nearly sixteen years, there are some other failure modes to be concerned about:

1. When reversing hard to get off a mud bank, it is possible to blow bits of shell or other grit up the stern tube and then wedging the seal open. Happened to some friends... they got off the bank, anchored and went to bed. Woke up for a pee call in the small hours and found ankle deep water over the sole. Tracked it down to a small bit of shell holding the face seal just a bit apart.

2. The bellows can fail, which can let copious leakage in. This can be due to ageing or some traumatic event, but whatever the cause, a LOT of water can get in... quickly!

But neither of these sorts of events are common, and at least the first type of failure is very easy and quick to remedy. The latter... not so easy, but our John Crane seal has an emergency blockoff clamp that will stop the ingress... but not allow shaft rotation when in use.

I think a perpetually dry bilge is worth the slight risk!

Jim
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Old 11-02-2019, 04:34   #10
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Re: Stuffing Box

Quote:
Originally Posted by Jim Cate View Post
While I am a convert to dripless seals, and have now used one for nearly sixteen years, there are some other failure modes to be concerned about:

1. When reversing hard to get off a mud bank, it is possible to blow bits of shell or other grit up the stern tube and then wedging the seal open. Happened to some friends... they got off the bank, anchored and went to bed. Woke up for a pee call in the small hours and found ankle deep water over the sole. Tracked it down to a small bit of shell holding the face seal just a bit apart.

2. The bellows can fail, which can let copious leakage in. This can be due to ageing or some traumatic event, but whatever the cause, a LOT of water can get in... quickly!

But neither of these sorts of events are common, and at least the first type of failure is very easy and quick to remedy. The latter... not so easy, but our John Crane seal has an emergency blockoff clamp that will stop the ingress... but not allow shaft rotation when in use.

I think a perpetually dry bilge is worth the slight risk!

Jim
Jim,

Thank you for the info! Very useful to know.
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Old 18-02-2019, 16:31   #11
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Re: Stuffing Box

The yard confirmed that it was dripless last week and also mentioned the burping procedure when splashing the boat after our haul out.
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