Are Dripless Shaft Seals Really Maintenance Free?

I don't know what the referenced article says, but dripless shaft logs are just about maintenance free. Like anything that rotates, the seal wears and when it fails it has to be replaced. But it might take several boat lives to get to that.

The only almost maintenance thing is that if you do not have a raw water flush hose attached to it, then when you relaunch after hauling for a bottom job or whatever, grab the flexible part and pinch it to let water fill the internal passages of the seal, sometimes called burping. Takes a few seconds after the boat is back in the water.

David

djmarchand said:

I don't know what the referenced article says, but dripless shaft logs are just about maintenance free. Like anything that rotates, the seal wears and when it fails it has to be replaced. But it might take several boat lives to get to that.

The only almost maintenance thing is that if you do not have a raw water flush hose attached to it, then when you relaunch after hauling for a bottom job or whatever, grab the flexible part and pinch it to let water fill the internal passages of the seal, sometimes called burping. Takes a few seconds after the boat is back in the water.

David

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I only had 7 years on the first PHI shaft seal, now replaced as recommended, but during that time there was nothing to maintain.

The problem is not she seal, it is the rubber bellows that holds the setup.

Most bellows are large enough to flood 4-5 bilge pumps worth ,,when it finally cracks.

With almost no maint , or water source required , the modern Duramax style packing solves the problem , with out the complexity , cost or the down flooding dangers.

I have a tides marine lip style seal and it IS maintenance free.

Gore packing is also just anout drip free and very low maintainance with no water flow issues to worry about.

bayview said:

Gore packing is also just anout drip free and very low maintainance with no water flow issues to worry about.

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Now is that the guy that invented the internet ?

The answer is. IT DEPENDS. On smaller shafts and motors(usually sail) pretty much dripless and free of maintenance same to be said for gortex or ultra x packing. Also on slower turning motors less trouble. On high powered high output units more complex with pressurized water fitting and more strain on billows. Oil and chemicals also affect life of billows. I and many others have discovered some of these units can be wet. There is also the ultimate higher risk of sinking if something goes wrong with seal and billows and this is not the case with standard packing boxes. This subject has been beat to death on multiple posts and sites. There are those who swear by the units and a few babes in the woods who believe they can have dry packing boxes with modern materials without the complexity or danger of the dripless units. There is of course heavy advertising for the dripless units. I am somewhat contrary and when ever I see heavy advertising campaigns my doubt genes start the process of critical questioning. My previous boat had PSI and it was wet and needed maintenance including new bellows. At high speed it was still wet. My present boat has two standard packing boxes with Duramax Ultra X packing and completely dry now for two years with zero maintenance. There is it appears to me a significant component of the boating population that are suckers for any product that promises less maintenance or easy use. IT'S A BOAT. My take on this ,not always popular, but I am not running for office is" If you can't take the heat stay out of the kitchen"(boat).

I've been involved in investigating a few local flooding events related to dripless seals. There are a few failure modes where the result is rapid flooding. No such risk with packing glands with modern packing material.

Many dripless tend to spray at high shaft rpm. We put spray deflectors on them to protect engine room air breathing equipment. Puts them in the "what's the point" category.

Bronze gland for me.

Ski in NC said:

I've been involved in investigating a few local flooding events related to dripless seals. There are a few failure modes where the result is rapid flooding. No such risk with packing glands with modern packing material.

Many dripless tend to spray at high shaft rpm. We put spray deflectors on them to protect engine room air breathing equipment. Puts them in the "what's the point" category.

Bronze gland for me.

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When I had my boat built I had my box enclosed ,with drains and pump, to keep things dry because previous PSI was wet at speed. Now I have a enclosed area which does nothing because bronze box with modern packing is dry. I believe the dripless to be a unnecessary questionably safe complication to shaft seal solutions. If the clear plastic box you see was on my previous boat with dripless it would be covered with crude from water. Note how clean and dry everything is.

To buck the "simpler is better" trend just a little, I am a big fan of dripless shaft seals. Having had experience with all three basic types (lip seal, bellows-type, and spring-loaded), my preference, without question, is the Lasdrop Gen II spring type.

The potential for a very bad flooding event has already been mentioned for the PYI (and other) seals where a flexible rubber bellows is used to keep pressure on the two faces of the seal. Otherwise, actually, these are not bad seals. Just keep an eye on the condition of the bellows, clamps and keep the seal faces clean.

The lip-type seals also work very well and eliminate the chances of a major flooding event due to the simplicity of the design (a rubber lip riding on the shaft). As a bonus, there is no occasional adjustment that must be made. The big disadvantage to a lip-type seal is that, eventually, it WILL wear a groove into your shaft. Once that groove becomes pronounced enough, the seal will leak. The only fix is either replacement of the shaft ($$$$) or, if you are lucky, you will be able to move the seal a bit to get back to a non-grooved section of the shaft. There are several ways to do this, but the biggie is that you must have enough room on the exposed part of the shaft (between the flange and the shaft tube) to move the seal location.

The best option, in my humble opinion, is the Lasdrop Gen II seals. These seals do not use a rubber bellows to put pressure on the seal faces, but rather use an internal spring. Go to their website for a much better explanation. As far as maintenance, as with any face-type seal, occasional cleaning of the seal faces may be necessary - but it is a simple task requiring only pulling the two faces apart (or potentially loosening the fixing clamp) and wiping carefully with a clean, soft rag, then readjusting the spring/bellows tension. If I was building a new boat - or refitting an older one, these are the shaft seals I would go with.

But, to answer the original question: "Are Dripless Shaft Seals Really Maintenance-Free?" Well, that has two answers: "Dripless?" Yes. But "Maintenance-FREE"? Nope. EVERYTHING on a boat requires SOME kind of maintenance!

ERIC

Profi-Seal is my favourite:

Profiseal

I hope it is both maintenance and drip free - time will tell.

They are all ok since the upgraded tech in conventional packing.

To say anyone is light years ahead of others is a stretch.

Anyone with experience of Volvo seals? Found some mostly positive info on CF, nothing here.