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Old 23-11-2020, 19:01   #1
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main drive thru hull seal

Dear All

I am purchasing a boat and it has the original thru hull seals currently 13 yrs old.

Some persons say you never need to change them unless there is signs of wear or water ingress.

Volvo penta says change every 7 years

What do the fleet of cat owners do?

Has anyone ever changed them? Has anyone ever done the change every 7 years?

What do cruisers think about this conundrum?

Do Insurance companies have their say?

Would love to hear what thoughts are out there, thanks, Dan
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Old 23-11-2020, 19:16   #2
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Re: main drive thru hull seal

Quote:
Originally Posted by Dan Morton View Post
Dear All

I am purchasing a boat and it has the original thru hull seals currently 13 yrs old.

Some persons say you never need to change them unless there is signs of wear or water ingress.

Volvo penta says change every 7 years

What do the fleet of cat owners do?

Has anyone ever changed them? Has anyone ever done the change every 7 years?

What do cruisers think about this conundrum?

Do Insurance companies have their say?

Would love to hear what thoughts are out there, thanks, Dan
Not completely sure what a "thru hull seal" is. Do you mean a stuffing box or a volvo dripless type shaft seal or something else ?
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Old 23-11-2020, 20:06   #3
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Re: main drive thru hull seal

Hi yes I mean the main seal the drive leg goes through, the main seal that keeps the water out of the boat
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Old 23-11-2020, 20:18   #4
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Re: main drive thru hull seal

The sail drive seal
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Old 23-11-2020, 21:23   #5
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Re: main drive thru hull seal

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Originally Posted by Dan Morton View Post
Hi yes I mean the main seal the drive leg goes through, the main seal that keeps the water out of the boat
Just to be sure ... are you now talking of a saildrive unit and not a shaft drive ?
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Old 24-11-2020, 08:44   #6
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Re: main drive thru hull seal

These articles may provide some clarification and advice:

“Troubleshooter: Understanding Shaft Seals” by Steve Zimmerman
https://www.passagemaker.com/technic...ng-shaft-seals

“Stuffing box inspection and replacement” ~ by Walter Garschagen
https://www.oceannavigator.com/stuff...d-replacement/

“Re-Packing A Traditional Stuffing Box”
~ by Rod “RC” Collins (Compass Marine)
https://marinehowto.com/re-packing-a...-stuffing-box/
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Old 24-11-2020, 09:53   #7
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Re: main drive thru hull seal

Saildrive-to-hull seals don't really wear. But they do age. They become brittle and start to develop cracks over time.
Volvo says to change them every 7 years because if they didn't say that, and a boat with 12 year old seals had them crack, leak, and sink the boat, you'd have:
Insurer: "So, owner, you never changed these seals?"
Owner: "No, we just followed the maintenance schedule in the manual, which didn't say to change them."
Insurer: "So, Volvo, are these seals known to fail with age? Yes? And yet you led the owners into thinking they last forever?"


By explicitly saying "the seal only lasts 7 years, so change it then", Volvo is trying to protect themselves from being sued by insurers when the seals fail and sink the boat. Since it's now a routine maintenance item, it's the owner's responsibility, and if it sinks the boat, the insurer will ask the owner "why didn't you follow the clearly-specified maintenance instructions for this thing?"
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Old 24-11-2020, 10:41   #8
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Re: main drive thru hull seal

Quote:
Originally Posted by GordMay View Post
These articles may provide some clarification and advice:

“Troubleshooter: Understanding Shaft Seals” by Steve Zimmerman
https://www.passagemaker.com/technic...ng-shaft-seals

“Stuffing box inspection and replacement” ~ by Walter Garschagen
https://www.oceannavigator.com/stuff...d-replacement/

“Re-Packing A Traditional Stuffing Box”
~ by Rod “RC” Collins (Compass Marine)
https://marinehowto.com/re-packing-a...-stuffing-box/

He's not talking about a shaft seal. He's talking about a sail drive leg boot. This is more relevant:


https://www.boats.com/reviews/all-about-saildrives/


To the OP: I would certainly respect the manufacturer's replacement interval, for the reasons outline in the linked article (mainly, insurance). These things DO fail from time to time, and sink boats. You don't want to be blamed for it because you exceeded the replacement interval. It's an expensive PITA, but goes with the territory of having sail drives.
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Old 24-11-2020, 11:29   #9
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Re: main drive thru hull seal

Quote:
Originally Posted by Dockhead View Post
He's not talking about a shaft seal. He's talking about a sail drive leg boot. This is more relevant:


https://www.boats.com/reviews/all-about-saildrives/


To the OP: I would certainly respect the manufacturer's replacement interval, for the reasons outline in the linked article (mainly, insurance). These things DO fail from time to time, and sink boats. You don't want to be blamed for it because you exceeded the replacement interval. It's an expensive PITA, but goes with the territory of having sail drives.
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Old 24-11-2020, 16:00   #10
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Re: main drive thru hull seal

I would spend some time reading up on how you change these seals. Usually there is a water sensor between two seals to act as a warning that the lower seal is leaking. Must confess my experience here comes from the last millennium. Things may have changed.
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