Shaft Seal - This Could Get Ugly...

[markpj23]

Many thanks for all the replies to this thread.

I took the shaft seal 'apart' meaning I slid the compression clamp / surface inboard away from the stern tube. I have to say that all looks very good. A little sign of salt water intrusion but nothing too bad in my opinion. Will try to post some pictures soon.

This is a Gen II Lasdrop unit and I admire its simplicity. Also my one email to the company support mailbox was answered by a return phone call within 2 hours - pretty darn good customer service in my book.

[hellosailor]

Elie, those carbon/stainless donut seals often work very well for a very long time. They are used in many applications including the ubiquitous automobile air conditioning compressors, where compressor seals are equally well known for failing suddenly and unexpectly.

So, take one great seal (of a design known to sometimes fail suddenly with no repair possible, only replacement) and one rubber bellows (and generally rubber part makers suggest replacements at five years of age, and keeping petrochemicals away from them), and you've got a great system that unfortunately has a couple of inconvenient failure modes.

As opposed to the low-tech stuffing box, which can be repeatedly snugged down to deal with leaks, and when re-packed with teflon or other synthetics instead of old cotton packing materials, can be rebuilt rather easily.

I think the high tech solutions were a great idea when they were first invented, but then when someone figured out "well, if we used better packing material, we could solve this problem for $20" I think the high-tech stuff got obsoleted.

Granted, it will never drip until it fails--but it still WILL FAIL unless there's some expensive routine maintenance on it. I guess that's the price of a bone-dry bilge, huh?<G>

[Maine Sail]

BOTH Dripless seals and traditional stuffing boxes use RUBBER HOSES or RUBBER BELLOWS and BOTH can and do fail and BOTH will need to be peridically replaced!

Here's a cracked traditional stuffing box hose:

[GordMay]

Originally Posted by hellosailor

... you've got a great system that unfortunately has a couple of inconvenient failure modes.
... Granted, it will never drip until it fails--but it still WILL FAIL unless there's some expensive routine maintenance on it. I guess that's the price of a bone-dry bilge, huh?<G>

Presuming he has a deck-stepped mast.

[GordMay]

FWIW:
I can highly recommend:
Acoustic's Sailing Photo Galleries
Maine Sailing's Photo Galleries at pbase.com

See his excellent Boat Projects Gallery:
Boat Projects Gallery Photo Gallery by Maine Sailing at pbase.com

[Maine Sail]

Thanks Gord! The check is in the mail???

These two are my latest:

Seacock & Thru-Hull Primer / Pre-Information

Replacing Thru-Hulls & Seacocks

[Joli]

Originally Posted by Acoustic

Thanks Gord! The check is in the mail???

These two are my latest:

Seacock & Thru-Hull Primer / Pre-Information

Replacing Thru-Hulls & Seacocks

I like your website and thank you for taking the time to publish it but.....

the fact that the Apollo mushroom does not have the web thickness of Groco seacock flange is not really a fair comparison. The Groco flange must hold the valve to the seacock base so it must be more robust. The Apollo mushroom is screwed into a complete seacock that is bolted to the hull, it does not see the same loading.

Maybe compare an Apollo Mushroom to a Groco mushroom? It seems disingenuous to slam Apollo like you are doing.

I have no financial stake in this and use both makes on our boats.

[Maine Sail]

Originally Posted by Joli

I like your website and thank you for taking the time to publish it but.....

the fact that the Apollo mushroom does not have the web thickness of Groco seacock flange is not really a fair comparison. The Groco flange must hold the valve to the seacock base so it must be more robust. The Apollo mushroom is screwed into a complete seacock that is bolted to the hull, it does not see the same loading.

Maybe compare an Apollo Mushroom to a Groco mushroom? It seems disingenuous to slam Apollo like you are doing.

I have no financial stake in this and use both makes on our boats.

Read it carefully! I'm in no way slamming Apollo only making a comparison between the two different methods and the given strength between the two common types of installations. The two common types of installations are

1) A proper flanged seacock through bolted or tapped into a solid fiberglass backing plate with the thru-hull treaded into it.

2) A thru-hull with a backing nut and a gate or ball valve screwed directly to it with NO FLANGE. This is how many, many production builders did it for years. Asside from the mismatching of thread types in this installation it is less robust and offers far less strength!



My point is that it's not as strong or safe to thread a ball valve directly to a thru-hull and that using a flanged adapter or a proper flanged seacock is far stronger. This is why I show the nominal thickness of both the thru-hull and the flanged adapters.

Threading a ball or gate valve directly to a thru-hull fitting is not the safest practice and as I've shown offers much less strength when compare to a proper seacock or a flanged adapter and a ball valve..


Hope that makes sense..

[David M]

Do it in this order:

Pull the shaft.

Determine if the shaft is bent.

While you are out...how are your rudder bearings/packing glans?

Replace the cutlass bearings.

Reinstall the shaft.

Install the dripless shaft seal.

Launch the boat

Have the yard align the engine and have them teach you how. Learn their tricks of the trade. Align the engine with the boat in the water..this is important because things move between when the boat is on the land and when the boat is in the water.

Run your engine for 50 hours underway with its normal load.

Re-align your engine after 50 hours of engine use.

[GordMay]

As Acoustic noted, he was advocating a proper flanged seacock through bolted or tapped into a solid fiberglass backing plate with the thru-hull treaded into it, not a particular manufacturer.

As it happens, Conbraco also makes “Apollo” seacocks (as do Groco, Buck Algonquin & others):
See their 78 series Full-Flow Sea Flange Valves
Apollo Valves :: Marine :: Ball valves

Note: The Groco (complete assembly pictured) include a Bonding Lug.

[Joli]

Originally Posted by Acoustic

Read it carefully! I'm in no way slamming Apollo only making a comparison between the two different methods and the given strength between the two common types of installations.

Acoustic, I understand what you are saying but you are comparing the thickness of a mushroom casting (Apollo)

http://i.pbase.com/g4/84/622984/3/91572913.VLzhy78u.jpg

to the thickness of a flange base.

http://i.pbase.com/g4/84/622984/2/91599396.hh4Wj2n6.jpg

that is not apples to apples.

The mushroom screws into the seacock base and does not have the load on it that the valve has when screwed to the top of the flange base.


I applaud the way you install seacocks, it is correct but it reads like the Apollo is inferior. The wall thickness of the Apollo mushroom does not need to match the wall thickness of the flange base since it does not have the load associated with carrying a valve.

And yes you are right. Many builders for years used a mushroom with a ball valve or worse a gate valve spun onto it. That why most boats that sink do so in their docks when left unatended.

OK, back to the regulary scheduled program. ie Marks engine, tranny, propshaft.

[Charlie]

Accoustic:

I think you should put up your own website or write a book. Your descriptions and pictures are beyond compare. I have read over and over how to change the stuffing box in other books. With the help of your pictures and prose it is really understandable. I also like the comparrison of the different types of thru hulls.

[Maine Sail]

Originally Posted by Joli

Acoustic, I understand what you are saying but you are comparing the thickness of a mushroom casting (Apollo)

http://i.pbase.com/g4/84/622984/3/91572913.VLzhy78u.jpg

to the thickness of a flange base.

http://i.pbase.com/g4/84/622984/2/91599396.hh4Wj2n6.jpg

that is not apples to apples.

The mushroom screws into the seacock base and does not have the load on it that the valve has when screwed to the top of the flange base.


I applaud the way you install seacocks, it is correct but it reads like the Apollo is inferior. The wall thickness of the Apollo mushroom does not need to match the wall thickness of the flange base since it does not have the load associated with carrying a valve.

And yes you are right. Many builders for years used a mushroom with a ball valve or worse a gate valve spun onto it. That why most boats that sink do so in their docks when left unatended.

OK, back to the regulary scheduled program. ie Marks engine, tranny, propshaft.

Joli,

I'm very sorry you read it that way. That article has been read well over 1500+ times and I've personally emailed and corresponded with over 50 people, regarding that article, and so far NOT ONE other person reads it the way you do.

Again, I am NOT COMPARING the Apollo to the Groco! I am comparing screwing a valve directly to a thru-hull and the resulting wall thickness that would result in doing so vs. the resulting wall thickness of using a flange or flanged seacock.

To show why a flanged base or a flanged seacock is stronger than screwing a valve directly to a flangeless thru-hull I also measured that thickness.

Here's exactly what I said in the photo of the thru-hull with the calipers:

"I am illustrating this to show why simply sticking a valve onto a thru-hull (without flange) is not as strong or as safe as using proper flanged seacocks and threading the thru-hull into a flange or thru-hull. Simply threading a valve directly to a thru-hull, with no flange, increases the risk that the thru-hull could be snapped off.
I personally had this happen to me when a spare alternator hit my ball valve that was screwed directly to a thru-hull and cracked it. This is the number one reason I will now only use properly flanged seacocks and thread the thru-hull into it."


If you don't get that I don't know what to say to help you understand..

[Kanani]

Originally Posted by markpj23

OK, so it's about time to tackle the newest problem that's come up. Looking for some tips from y'all before I dive in....

Clue #1: Previous owner had told me a story about how his bellows-type shaft seal started leaking while underway - and he couldn't get it to stop. So he had it replaced with a new type Lasdrop carbon seal unit. Purchase survey said the running gear was fine (don't they all say that?)

Clue #2: PO says the guy came down and installed the new seal while they were still waterborne. Hmmm.... the Lasdrop instructions say that's a no-no...

Clue #3: When the shaft is turning I can visibly see runout at low RPM. Seems to settle out at higher RPMs but is still there. I wonder if that's more than just normal thrust torque I'm seeing... Does not seem to be more or less than the way it was when we bought the boat.

So fast forward about 100 hrs of motoring later. I take the boat to haul out, get her a haircut and then splash again. Quick 1-day round trip.

Clue #4: While she's hanging in the slings, I turn the prop by hand and feel a resistance through one portion of the circle - seems to be about 30 degrees of rotation where things bind up a bit. Doesn't seem real bad but enough for me to notice.

So, splash back in and boy she moves faster through the water now with the clean hull! But yikes, the shaft seal leaks.

Clue #5: Seal leaks LOTS when under load. Bilge pump keeps up just fine but I really don't like water coming into the people tank like that. While at low / no RPM all is dry (thankfully).

Clue #6: No abnormal vibration heard / felt after the haul-out. All seems the same except for the leaking shaft seal.

Clue #7: Come to think of it, the engine used to spin happily up to 3200 RPM under load. Now I get black smoke and increasing temp around 2200 RPM. She will not go past 2300.... this can't be good. However, prior to the haul-out this was also true.

So now it's time to repaint the bottom and address the seal issue. As I've thought about it, the scenarios could be (from least to most severe):

a) Since the new seal was installed while waterborne, I just need to readjust it properly while out of the water this time.

b) I need to re-align the shaft and then readjust the seal. If the resistance is gone when I turn the prop after that, then all is fine.

c) The new seal is toast and will have to be replaced. Nothing else really wrong. Will have to break the coupling to replace the seal, then realign the shaft.

d) The motor mounts are sagging and will have to be replaced if I'm ever going to get the shaft run-out down to spec. (By the way - how much run-out is acceptable?)

e) The cutless bearing is shot and is the cause of misalignment / seal leakage.

f) The shaft is bent / warped and it trashed the cutless bearing so bring a big check book....

Being the newbie that I am, I've never done an alignment before and don't have the gages or mounts I'd need. Will probably hire that done but wouldn't mind doing it myself.

Any thoughts / tips / probable causes you folks can share? As always, many thanks in advance for your replies!

Hey Mark,

What happened to this job

It didn't kill you did it???

I'm dying to hear how it went. I hope it had a happy ending.

[markpj23]

I pulled the compression housing back away from the stern tube seal and found everything to be in good shape. I should note that on the trip to the yard we did not leak a bit.

I've also removed the static portion of the seal from the stern tube hose and slid that forward. There is some calcium build-up on the shaft but nothing looks amiss. I will clean it all up with some emery cloth (not the seal surfaces of course), wipe the carbon seal surface clean and reassemble.

I think all I had was some critter contamination.

Shaft looks fine. Had the cutless bearing replaced and got 2 different mechanics recommendation to leave things alone as they see no issues.

Regarding the black smoke, I'm becoming more and more convinced that I'm over-propped and have been since we bought the boat.

Some days during the refit are better than others....