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Author Topic: Zinc question  (Read 337 times)

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Analgesic

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Zinc question
« on: October 08, 2018, 08:20:52 AM »

Last Winter I replaced the PSS Shaft Seal bellows which involved disconnecting and reconnecting the shaft to the flexible coupling.  There is a wire that jumps metal to metal around the coupling.  This morning I hauled the boat for the season and noted the two shaft zincs looked as good as new, not the sacrificial decaying look I'm used to seeing at season's end.  The shaft itself looks okay at first glance.   I have to assume the bridging wire is bad.  I haven't checked the pencil zinc in the heat exchanger yet.  Anyone know if I need to be looking for other sacrificial metal trouble in the engine or elsewhere?   
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Brian McPhillips

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Re: Zinc question
« Reply #1 on: October 08, 2018, 08:26:04 AM »

Brian.
Rather than ass/u/me anything, check resistance between the two sides of the coupling. Then worry about it if continuity is broken.

-k
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mark_53

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Re: Zinc question
« Reply #2 on: October 08, 2018, 09:02:38 AM »

If your zincs arn't doing their job the next less noble metal is your bronze prop.  Check it for pitting.
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Ron Hill

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Re: Zinc question
« Reply #3 on: October 08, 2018, 02:03:03 PM »

Brian : I've had a flexible coupling for about 30 years - it isolates the drive shaft from the engine ground. 
In those years I've never had a problem with erosion of the shaft (bronze then changed to stainless) or the bronze prop.

If your shaft Zns are not eroding - I guess that they may of not made contact.  I always paid the little bit extra to purchase the shaft Zn with the embeded "BB" on the inside (toward the shaft).  When I mounted that Zn on a place on the shaft that I "shined up", I turned the hex screws tight on each side. Then I hit the Zn with a hammer, rotated the shaft and hit the other side.  Then retightened both of the screws.  Did that twice!!

A few thoughts
« Last Edit: October 09, 2018, 01:25:49 PM by Ron Hill »
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Noah

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Re: Zinc question
« Reply #4 on: October 08, 2018, 03:32:21 PM »

Make it a light tap. Not a good idea to hammer too hard on your prop shaft. Here is MaineSailís helpful article on zinc install.
https://marinehowto.com/anode-installation-best-practices/
« Last Edit: October 08, 2018, 05:50:26 PM by Noah »
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Ron Hill

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Re: Zinc question
« Reply #5 on: October 09, 2018, 01:28:29 PM »

All : I didn't say "Hit it with a sledge hammer". 

A thought
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patrice

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Re: Zinc question
« Reply #6 on: October 11, 2018, 10:32:19 AM »

Hi.
Also to check anode is made of proper material.
If you re in salt water or not.
Material should be different.
I don t remember wich is wich.  If someone can jump in..
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Dave Spencer

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Re: Zinc question
« Reply #7 on: October 11, 2018, 10:49:08 AM »

Zinc for salt water.  You will get disappointing results in fresh water.
Aluminum for brackish water although it's also suitable for use in salt and fresh water.
Magnesium in fresh water, but not in salt water.

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Dave Spencer
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Analgesic

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Re: Zinc question
« Reply #8 on: October 12, 2018, 09:24:48 AM »

Just got a look at prop (3 blade fixed) and I do see some pitting which is concerning, will need to remove and polish off metal paint for closer inspection.  I have the zinc for salt water and installation  was done using proper method described.  I'll trouble shoot the bridging wire, pencil zinc in heat exchanger and look for other trouble this weekend. 
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Brian McPhillips
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