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Old 05-14-2019, 03:59 PM   #21
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Originally Posted by Bkay View Post
How am I supposed to know that? Just kidding - but not really.

I'm not sure how you are set up, I would assume that you would want no connection between the tube and the shaft.

Having said that, you mentioned a green bonding wire, that tells me you have a bonding system and the stern tube is attached to a hull zinc somewhere.
Heh. Me too.

I've been thinking no connection, with shaft "floating" inside the tube. We'll see; haven't heard from my guru yet.



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Now that I think about it, you can check the continuity of the two stern tubes. If they have good continuity, then at least those two items are connected (even if they are not connected to the rest of the bonding system). If they are connected, they should be corroding at similar rates. If there is no connection, get help trouble shooting your bonding system.

If you find good continuity and no other sign of galvanic corrosion - I might not loose any sleep over the fact that one is tarnishing and the other is not.
I'm hoping to check both... and then hoping they're roughly equal. Connected, not connected, whatever... roughly equal readings would seem good. I think. If not about the same, then that might mean one or the other is/is not connected... or it might mean one is deteriorating at a different rate. I think. (Thinking out loud here, a bit.)

I'll digress a bit...

The part I'm struggling with now is visualizing what's behind the flange, and how the tube is connected. The bonding wire is connected to the flange, but if this is a two-part assembly (separate tube and flange), then I don't see a way that bonding wire would have anything to do with the tube itself.

But then I also can't figure out how water would be coming in at the mounting studs. IF IF IF the tube is fully glassed into the hull, then I'd expect no water between tube and fiberglass, hence no water to leak through the mounting studs in the flange. In this case, I don't see what the flange accomplishes; it doesn't appear to be load-bearing.

OTOH, IF IF IF the tube is "sealed" into the hull (4200, 5200, whatever) then (some of) that could have failed I guess... which would mean water ingress is possible... and maybe the flange is meant to be an extra sealing surface...

Maybe.

Anyway, the part that got my attention most is the amount of verdigris that had "dripped" (?) down under the tube and onto the inside of the hull under there. I didn't get a pic of that before I at least cleaned it up a little, and it was actually easy to wipe most of it up quickly with a dry rag... but that too was another symptom that was so much different from the other side.

Hoping to hear from my guru soon.

-Chris
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Old 05-14-2019, 04:02 PM   #22
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I'd replace the rusted hose clamps with better quality.
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Originally Posted by ranger42c View Post
Yeah, they're a little unsightly. They're ABA clamps, though.
Sorry, I mis-spoke, a little. The large clamps on the blue hose are AWAB/ABA style. Looking more at the smaller hose clamps on the water feeder lines aren't... and yep, I'll be replacing those with better. Thanks again for making me look at it.

-Chris
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Old 05-14-2019, 04:04 PM   #23
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Mr. r. Yes. Quite familiar with Brasso. Good stuff for brass and copper alloys. Also good for polishing headlight lenses/plastics due to it's mild abrasive qualities. Cleaning of oxidized surfaces is effected more by mechanical means (rubbing) than by chemical means although there IS some chemical removal of oxides.

I looked up the MSDS for Brasso and it contains, as I suspected from the smell, amonia as well as oxalic acid.

Maybe the 3M stuff works more "chemically"? I expect I'll slog on with the Brasso since it's working sorta kinda. I'll see how I feel about that after my next session...

-Chris
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Old 05-14-2019, 06:09 PM   #24
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I'm along with Bk on this one. I have been known to swap out the SS HW with SB, especially when its submerged duty in contact with bronze. The view of the clamps looks good, and they appear to be the euro versions with rolled edges. Nice..

If you want, try some cheap Italian tomato sauce on the green bronze. Let us know if we can squash that internet rumor that it works well.
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Old 05-14-2019, 06:57 PM   #25
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Greetings,
Mr. dd. I've also heard Ketchup works on tarnish.



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Old 05-15-2019, 03:02 PM   #26
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I'm along with Bk on this one. I have been known to swap out the SS HW with SB, especially when its submerged duty in contact with bronze. The view of the clamps looks good, and they appear to be the euro versions with rolled edges. Nice..

If you want, try some cheap Italian tomato sauce on the green bronze. Let us know if we can squash that internet rumor that it works well.
SB?

I thought about trying the ketchup/catsup, but we haven't really stocked our boat fridges yet so didn't have any on hand. I suspect the Brasso might have been cheaper.



Did some poking around with the multi-meter, inconclusive results. I have continuity between shaft and tube, shaft and flange, tube and flange... on both sides. O Ohms resistance on the starboard shaft/tube, about 1.2 Ohms on the port shaft/tube (port being the one in question). No clue whether ~1.2 Ohms is significant, or relevant.

In our owners forum, I'm told the tube and flange are indeed separate, and the shaft is free-floating (so to speak) within the tube (i.e., supported by the gear at one end and by the two struts with cutless bearings toward the other end).

-Chris
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Old 05-15-2019, 05:15 PM   #27
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Originally Posted by ranger42c View Post
I have continuity between shaft and tube, shaft and flange, tube and flange... on both sides.

Have to admit, I haven't figured out HOW we have continuity between shaft and tube, shaft and flange, and tube and flange...

They're not actually touching each other (assuming tube and flange are separate pieces, as I was recently told), at least anywhere in the general vicinity...

-Chris
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Old 05-15-2019, 06:35 PM   #28
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Greetings,
Mr. r. I can't see how the flange and tube CAN be separate pieces. What is holding the tube in place if not the flange?
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Old 05-15-2019, 07:42 PM   #29
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How it goes together

The shaft log consists of an integral fiberglass molding with a bolted bronze thru-hull pushed through from the outside. The square plate you see is backing for the bolts.

You should have very good connections (<1ohm) between all the metal parts. If a part is corroding more rapidly than the others check its bonding connection.

Bonding is easiest checked while on the hard using a multimeter between the parts. In the water a long lead with a good connection to the bonding buss or DC negative to compare all fittings. High resistance connections would be requesting attention. "Normal" will be a little different depending on your particular circumstance but I thing you would find a pattern after a few checks and be able to determine what is "normal".

I was investigating a potential corrosion issue on a Californian a year or so ago using a silver chloride half cell. All the parts I checked were around -550mv (protected) except for the stbd V-strut which was at -250mv (bronze no zinc value). Told me that bonding was good except for the V-strut which was unprotected due to a poor bonding connection.
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Old 05-16-2019, 06:57 AM   #30
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Greetings,
Mr. r. I can't see how the flange and tube CAN be separate pieces. What is holding the tube in place if not the flange?
Same here, but see next...


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Originally Posted by bglad View Post
The shaft log consists of an integral fiberglass molding with a bolted bronze thru-hull pushed through from the outside. The square plate you see is backing for the bolts.

You should have very good connections (<1ohm) between all the metal parts. If a part is corroding more rapidly than the others check its bonding connection.

Bonding is easiest checked while on the hard using a multimeter between the parts.
I guess I can envision the flange holding something inward, pulling inward toward the boat/engine/etc. Not obvious in the interior pics... nor in the exterior pics I have of the hull, but then I wasn't aware of that so wasn't aiming specifically in that area. Thanks.

We'll be hauled shortly, so I'll be able to check bonding better. I take it the ~1.2 Ohms resistance I measured between port shaft and port tube is right on the edge of significant. yes?

-Chris
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Old 05-16-2019, 07:16 AM   #31
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SB?

I thought about trying the ketchup/catsup, but we haven't really stocked our boat fridges yet so didn't have any on hand. I suspect the Brasso might have been cheaper.



Did some poking around with the multi-meter, inconclusive results. I have continuity between shaft and tube, shaft and flange, tube and flange... on both sides. O Ohms resistance on the starboard shaft/tube, about 1.2 Ohms on the port shaft/tube (port being the one in question). No clue whether ~1.2 Ohms is significant, or relevant.

In our owners forum, I'm told the tube and flange are indeed separate, and the shaft is free-floating (so to speak) within the tube (i.e., supported by the gear at one end and by the two struts with cutless bearings toward the other end).

-Chris


Sorry SB = silicon bronze.
Got to be careful measuring from metal to metal when there may be galvanic voltage present. A small dmm uses ohmmeter voltage source not much stronger than the existing voltage present. If V is present, the Ohm readings will not be correct.
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Old 05-16-2019, 07:29 AM   #32
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Conductivity of water

In this case yes. You will know better when you are on the hard. It may actually be worse than 1.2 ohms. For example, Volvo Penta Saildrives are supposed to be isolated which you can prove out of the water. But, once the system is submerged it will no longer test that way due to conductivity of the water.

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We'll be hauled shortly, so I'll be able to check bonding better. I take it the ~1.2 Ohms resistance I measured between port shaft and port tube is right on the edge of significant. yes?

-Chris
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Old 05-16-2019, 08:08 AM   #33
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Greetings,
From an independent source:


WTF are those people going on about? What is the insulation resistance between 3 angels dancing on the head of a pin?



The photo shows a relatively large leak due to poor sealing between the flange, stud, and the void space behind the flange which is flooded. The moron "surveyor" completely ignored the obvious and pointed out a non issue.


The condition of the stud and its hull side threads should be determined and the flange should be resealed.


This issue has absolutely zero to do with bonding or the resistance of connections.


How on Earth did a question about something that has no impact on anything other than what should have been no more than idle curiosity turn into a sky might be falling corrosion thread?




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Old 05-16-2019, 09:19 AM   #34
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I seem to recall the maximum resistance between two items protected by the bonding system is 1 ohm. Seems like that's a tough standard to maintain (the source was either a Pro Boat article or something Steve D' wrote.)

Regarding:

Quote:
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How on Earth did a question about something that has no impact on anything other than what should have been no more than idle curiosity turn into a sky might be falling corrosion thread?
Good point. But my position is: 1) you should check bonding on a regular basis, 2) corrosion should be an easy problem to rule out and once ruled out you can focus on other solutions, 3) I've seen may small problems become big problems by ignoring evidence.

If it takes the OP a while to figure out how to perform the checks to rule it out - at the end of the process he has added a necessary skill. That's not a bad outcome either.
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Old 05-16-2019, 09:54 AM   #35
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If corrosion on metal is annoying, clean it off and paint it with Le Tonkinois varnish.
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Old 05-16-2019, 01:05 PM   #36
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Originally Posted by RT Firefly View Post
The photo shows a relatively large leak due to poor sealing between the flange, stud, and the void space behind the flange which is flooded.

The condition of the stud and its hull side threads should be determined and the flange should be resealed.

This issue has absolutely zero to do with bonding or the resistance of connections.
That's useful, thanks. I can't quite picture "the void space behind the flange" though; looks like solid fiberglass to me...



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If it takes the OP a while to figure out how to perform the checks to rule it out - at the end of the process he has added a necessary skill. That's not a bad outcome either.
I think I'm learning... although perhaps at glacial pace.

I expect I'd understand better/faster if I had a clue what the parts (stern tube, flange, etc.) look like when they're not in a boat, but I haven't tacked that down yet.

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Old 05-16-2019, 01:45 PM   #37
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I expect I'd understand better/faster if I had a clue what the parts (stern tube, flange, etc.) look like when they're not in a boat
-Chris
https://www.tidesmarine.com/shaftseals/locator.php

Don't know if the graphic on this page helps visualize it or not...

I've spent many hours climbing around the bowels of my boat and don't consider any of it a waste of time. Well, OK a little of it was a waste of time.
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Old 05-16-2019, 03:00 PM   #38
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Quote:
Originally Posted by RT Firefly View Post
Greetings,
From an independent source:


WTF are those people going on about? What is the insulation resistance between 3 angels dancing on the head of a pin?



The photo shows a relatively large leak due to poor sealing between the flange, stud, and the void space behind the flange which is flooded. The moron "surveyor" completely ignored the obvious and pointed out a non issue.


The condition of the stud and its hull side threads should be determined and the flange should be resealed.


This issue has absolutely zero to do with bonding or the resistance of connections.


How on Earth did a question about something that has no impact on anything other than what should have been no more than idle curiosity turn into a sky might be falling corrosion thread?




LOL. Thanks for the laugh. About time someone said something. [emoji3]
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Old 05-16-2019, 03:03 PM   #39
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Greetings,
From an independent source:

WTF are those people going on about? What is the insulation resistance between 3 angels dancing on the head of a pin?

I dunno; but if you can provide the test subjects, I do have the correct meter.
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Old 05-16-2019, 04:23 PM   #40
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https://www.tidesmarine.com/shaftseals/locator.php

Don't know if the graphic on this page helps visualize it or not...

I've spent many hours climbing around the bowels of my boat and don't consider any of it a waste of time. Well, OK a little of it was a waste of time.
Yeah, I had that one already... but that the shaft seal and not where the apparent leak is coming from. That said, I just got the engineering drawings for the "shaft log" (their terminology, not "stern tube") and now I've got a slightly better clue about what the thing is and how it's in there.

And FWIW, what I've been calling a "flange" is actually the internal "backing plate" -- so the tube that goes through there has it's own flange as part of the casting, but that's hidden by the backing plate that's visible in the pic.

They were also kind enough to give me a quick run-down about how to remove, inspect, reseal, replace the shaft log... so now I know maybe 1000% more than I did this morning.

A bunch of work though, and maybe an OK time to replace the Tides shaft seal, a hole bunch of hose clamps, and some hoses while I'm at it.

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