Education in Zinc Replacement Needed - Boat is fresh water only.

V

VerBoatin

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Apr 17, 2012
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I need to replace the zinc on my boat shown in the photograph below taken just a few weeks ago during the haul-out hull inspection. Would you kindly advise what type of replacement zinc is required to replace the existing zinc on this fresh water only boat? The center zinc is the one requiring two bolts but is there a specific model, part number, etc? The boat is a 1990 Wellcraft 3400 Gran Sport (34'). Also, the rudder units I am finding on line are listed as: R2, R3, R4...are they simply larger with the higher the numbers? I also read magnesium is used for fresh water and zinc for salt water boats? Thanks in advance for the assistance! VB
Transom Zinc.jpgRudder and Prop Shaft Zinc.jpg
 
D

dmccaffrey

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Re: Education in Zinc Replacement Needed - Boat is fresh water only.

VerBoatin said:
I need to replace the zinc on my boat shown in the photograph below taken just a few weeks ago during the haul-out hull inspection. Would you kindly advise what type of replacement zinc is required to replace the existing zinc on this fresh water only boat? The center zinc is the one requiring two bolts but is there a specific model, part number, etc? The boat is a 1990 Wellcraft 3400 Gran Sport (34'). Also, the rudder units I am finding on line are listed as: R2, R3, R4...are they simply larger with the higher the numbers? I also read magnesium is used for fresh water and zinc for salt water boats? Thanks in advance for the assistance! VB
View attachment 149533View attachment 149534
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The big center zinc kind of looks like one of these:

http://www.boatzincs.com/azhc-2.html
http://www.boatzincs.com/azhc-5.html

My guess would be the azhc-5. But it's hard to judge the size from that picture.

As for the rudder units, the numbers given are the diameter of the anode: R2 = 2", R4 = 4", etc.
 
Thalasso

Thalasso

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Re: Education in Zinc Replacement Needed - Boat is fresh water only.

VerBoatin said:
I need to replace the zinc on my boat shown in the photograph below taken just a few weeks ago during the haul-out hull inspection. Would you kindly advise what type of replacement zinc is required to replace the existing zinc on this fresh water only boat? The center zinc is the one requiring two bolts but is there a specific model, part number, etc? The boat is a 1990 Wellcraft 3400 Gran Sport (34'). Also, the rudder units I am finding on line are listed as: R2, R3, R4...are they simply larger with the higher the numbers? I also read magnesium is used for fresh water and zinc for salt water boats? Thanks in advance for the assistance! VB
View attachment 149533View attachment 149534
Click to expand...

Any anodes you put on, weather it be rudder or shaft anodes they need to be Magnesium. I doubt you will find a transom anode in magnesium. If you are in fresh water only you shouldn't have any galvanic corrosion do to dissimular metal. Your props, rudder and shafts are bronze. I boat with a guy who has v drives on a 33 Silverton and in the last 7 yr's he hasn't changed a thing and no problems. We boat in fresh water. If you can't find a magnesium transom anode and want to put one on, put a aluminum one on. Zinc will have no protection whatsoever in fresh water. West Marine carries aluminum transom anodes.About $35.00. If anything i would have a Galvanic Isolator if you don't have one already.
 
Fireman431

Fireman431

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Re: Education in Zinc Replacement Needed - Boat is fresh water only.

As far as the transom zinc, don't worry about the shape. Measure the center holes and go with that dimension. When replacing the anode, make sure the bonding surface is clean and corrosion free.

When you say 'fresh water', are you sure it's fresh and not brackish? Just verify before you switch out. Salt water gets zinc. Brackish gets zinc or aluminum. Fresh gets magnesium.
 
V

VerBoatin

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V

VerBoatin

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Re: Education in Zinc Replacement Needed - Boat is fresh water only.

Excellent information...thank YOU very much! If you don't mind, would elaborate on the galvanic isolation. I'm not familiar with such systems? Thanks much VB
 
V

VerBoatin

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Re: Education in Zinc Replacement Needed - Boat is fresh water only.

Good point! Let me elaborate. The boat is on a lake in Texas. That would be classified for the purpose of this discussion as freshwater, yes? Please feel free to provide correction, I appreciate the information! Thanks VB
 
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TilliamWe

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Re: Education in Zinc Replacement Needed - Boat is fresh water only.

You are getting good advice so far. Except for Thalasso's statement that galvanic corrosion doesn't happen in freshwater. It does. Where you keep the boat, the structure of the docks, the conditions of the dock/electric hookups, and the boats around you will all contribute to corrosion.
As long as your lake in Texas has an outlet, and isn't connected directly to the Gulf of Mexico, it's fresh water.
 
Thalasso

Thalasso

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Re: Education in Zinc Replacement Needed - Boat is fresh water only.

TilliamWe said:
You are getting good advice so far. Except for Thalasso's statement that galvanic corrosion doesn't happen in freshwater. It does. Where you keep the boat, the structure of the docks, the conditions of the dock/electric hookups, and the boats around you will all contribute to corrosion.
As long as your lake in Texas has an outlet, and isn't connected directly to the Gulf of Mexico, it's fresh water.
Click to expand...

I think you should reread my post. Nowhere did i say galvanic corrosion doesn't happen in fresh water. What i did say is
Any anodes you put on, weather it be rudder or shaft anodes they need to be Magnesium. I doubt you will find a transom anode in magnesium. If you are in fresh water only you shouldn't have any galvanic corrosion do to dissimular metal. Your props, rudder and shafts are bronze. I boat with a guy who has v drives on a 33 Silverton and in the last 7 yr's he hasn't changed a thing and no problems. We boat in fresh water. If you can't find a magnesium transom anode and want to put one on, put a aluminum one on. Zinc will have no protection whatsoever in fresh water. West Marine carries aluminum transom anodes.About $35.00. If anything i would have a Galvanic Isolator if you don't have one already.

The previous boat i had for 4yrs. This boat 6yrs. Both I/O's and in fresh water connected to shore power and by steel poles and other boats. One drive was Bravo III's and this one is Volvo DPS. Absouloutly no corrosion in either one. I think i have a little bit of a handle on how things work.
Read the third paragraph
www.boatus.com/boattech/MarineCorrosion.htm
 
Thalasso

Thalasso

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Re: Education in Zinc Replacement Needed - Boat is fresh water only.

VerBoatin said:
I need to replace the zinc on my boat shown in the photograph below taken just a few weeks ago during the haul-out hull inspection. Would you kindly advise what type of replacement zinc is required to replace the existing zinc on this fresh water only boat? The center zinc is the one requiring two bolts but is there a specific model, part number, etc? The boat is a 1990 Wellcraft 3400 Gran Sport (34'). Also, the rudder units I am finding on line are listed as: R2, R3, R4...are they simply larger with the higher the numbers? I also read magnesium is used for fresh water and zinc for salt water boats? Thanks in advance for the assistance! VB
View attachment 149533View attachment 149534
Click to expand...

Go to this site. There is a good explanation of Galvanic Corrosion.
www.boatus.com/boattech/MarineCorrosion.htm
 
V

VerBoatin

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Re: Education in Zinc Replacement Needed - Boat is fresh water only.

Yes, understood...its a fresh water only lake...no Gulf connection...VB
 
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