Adding external zinc

Nov 26, 2008
1,966
Endeavour 42 Cruisin
I'm contemplating hanging an additional zinc over the side to extend the life of my other zincs. I have one on my Maxprop and one on the prop shaft. The Maxprop zinc usually goes first.

I need to get this additional zinc connected to the bonding system. I can run a bonding wire from the main point where all my bonding comes together up to the mounting bolt of a stanchion base. Then clip a wire with the zinc onto the stanchion base. This will negate the need to penetrate the hull or deck with a wire.

Any issues with bonding the stanchions? I have a Stainless Steel bar between two stanchions with a solar panel mounted to the bar so the panel would be bonded.

Anything else to consider with adding an over-the-side zinc?

How do I know this zinc will sacrifice first?
 
Oct 22, 2014
20,995
CAL 35 Cruiser #21 moored EVERETT WA
Gettinthere do you believe it is your boat or the marina that has the stray DC current eating your zinc's.
 
Nov 26, 2008
1,966
Endeavour 42 Cruisin
I cruise full time. So I am in different conditions all the time. Sometimes motoring, sometimes sailing, sometimes at anchor, rarely at a marina. Warm water, cold water, clean water, silty water, salt water, brackish water, fresh water. So there is no pattern to the wear on my zincs, the only way to know is to dive. Would be much easier to pull up the wired zinc and check it.
 
Oct 22, 2014
20,995
CAL 35 Cruiser #21 moored EVERETT WA
Would be much easier to pull up the wired zinc and check it.
Yes. Just not sure if it will provide the assurance that your prop zinc is OK.

If the current is bad enough to eat a dropped zinc, it will be eating everything in the water. So most likely you will still need to dive or rig your camera (iPhone) to take an underwater picture of your prop and the zinc. I have used my iPhone in a water proof container attached to the boat hook. Others use a water protected camera (i.e Go Pro) When I first saw a guy using his GoPro to inspect the bottom of the boat I thought that was about the best use I have seen for a GoPro.

There was a forum message that talked about checking the DC current in the water around your boat in the past 6-8 months. Might be worth a look.
 
Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
I read somewhere that the zinc needs to be near whatever you need to protect and water speed/current erodes the zinc quicker. So hanging a fish would only give minimum protection to whatever it’s near, I clipped one to the back stay which did nothing. The zinc on the shaft are a lot closer to the prop than any fish would be. My Maxprop also uses zinc fast which makes sense if it’s moving through the water. Never understood the zinc on the outboard attached to the aluminum casing.

All U Get
 

SG

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Feb 11, 2017
1,670
J/Boat J/160 Annapolis
If you want an zinc "Grouper" or whatever, I'd put a copper or solid bronze post in one of the convenient lockers, run a marine grade (green) #12 or #14 wire from a GOOD Ground on the engine to the post. (just because I'm into overkill :^)))) Then I'd connect the zinc that you plan to drop to that.

Since you are having some signs of stray current corrosion....As for your through hulls, if you have metal (bronze) ones, I'd check those to see that they're okay, that the wires that link them to the ground have continuity and aren't corroded so as to be worthless. Even marine grade wires that are tinned corrode in a salt water environment. The insulation is air permeable enough to work on the conductors over time.
 
Sep 23, 2009
1,475
O'Day 34-At Last Rock Hall, Md
Just don't get your shaft zinc too close to the prop. Less than 12 inches to the forward surfzce of the strut may block cooling water to the cutless bearing. FYIW, you may fnd that you can feel the shaft zinc with your foot while foating at anchor. I keep two zincs on the prop shaft replacing one every year.
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Expecting a properly working zinc to last a year isn’t going to get it. You are going to have to short haul, swim or pay a diver and get those zincs replaced. A MaxProp is way too expensive to experiment with.
 

SG

.
Feb 11, 2017
1,670
J/Boat J/160 Annapolis
As Gunni says, that little zinc in most marinas and with most systems would only last a matter of months in the water if it's the only zinc. If you have an "over the side or stern" zinc, plus a shaft zinc, then the max prop's will last longer.

You have an expensive prop and shaft (and other parts) -- and you are noticing that the zincs are working. IT's really a lot cheaper protection that to be sorry later.
 
Nov 26, 2008
1,966
Endeavour 42 Cruisin
I dont expect a zinc to last a year, although when I was in fresh water, they lasted multiple years.

I would like one zinc, that I can put over the side to be the first in line to sacrifice, which will extend the life of the other two zincs. The Maxprop zinc always goes faster than the shaft zinc that is right next to the prop.

Regardless of whether I can check the prop zinc with a gopro, the ultimate goal is to slow down the maxprop zinc erosion whenever anchored, moored or docked.
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
I dont expect a zinc to last a year, although when I was in fresh water, they lasted multiple years.
Zincs last a long time in freshwater because they don't offer any protection. In fresh water, zincs form a hard coating that effectively insulates the zinc from any electrical activity. Thus they don't sacrifice. In freshwater, aluminum or magnesium are much more effective.

Rather than throwing more sacrificial anodes at the problem, it might be prudent to find the electrical pathway that is causing the rapid decay.
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
You only hope that a fish zinc on a wire will extend the life of your prop zinc. My experience was that it did nothing and it now resides in a landfill. The MaxProp zinc will go faster if it is doing it’s job, it protects a big piece of bronze. You can help it out by shining up the backside of the MaxProp and slapping a shaft zintight to the back of the prop body. This is a zinc after 8 months in the water, note the prop zinc is way more eroded than the shaft zinc. 5F967B46-B75E-436F-8E38-228B561DBEB9.jpeg
 
Nov 26, 2008
1,966
Endeavour 42 Cruisin
You only hope that a fish zinc on a wire will extend the life of your prop zinc. My experience was that it did nothing and it now resides in a landfill. The MaxProp zinc will go faster if it is doing it’s job, it protects a big piece of bronze. You can help it out by shining up the backside of the MaxProp and slapping a shaft zintight to the back of the prop body. This is a zinc after 8 months in the water, note the prop zinc is way more eroded than the shaft zinc. View attachment 145293
This looks very similar to my setup, short shaft with a donut zinc on it but not hard up against the prop. I have a shaft shark against the prop and then the donut zinc up the shaft from that.

Because I move around all the time, there is no pattern to the wear. Sometimes the zinc lasts a long time and sometimes it doesnt. Likely because of intermittent external sources of electrolysis as I travel.
 

Gunni

.
Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
I found that installing a galvanic isolator helped a lot with zinc erosion. But you have to have a steady rate of erosion on your anode. The archives here are full of stories from people who brag about how long their zinc lasts...years, when in fact their zinc has been salted-over and quit working. I switched to aluminum anodes years ago because I move between brackish and saltwater (picture above). Get an 8 month season out of them, could probably stretch that to a year but when the MaxProp zinc comes off it has the ability to snap the mounting bolts off in the prop body. This leads to a drill and tap mess.
 
Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
Cruising with a boat with so many dissimilar metals through waters with variable salinity negates any comparison to a Boat that sits in the same slip for three months then gets hauled for the winter.

All U Get
 
Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
. Get an 8 month season out of them, could probably stretch that to a year but when the MaxProp zinc comes off it has the ability to snap the mounting bolts off in the prop body. This leads to a drill and tap mess.
Are you talking about the three stainless screws? So are they using the aluminum to fuse together?

All U Get
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
The MaxProp anode has very narrow amounts of material around the attaching bolts. As the anode erodes it comes free of the bolts and rotates into the area where the blades can strike the anode. The anode then either snaps off clean or takes the remaining attachment bolts with the anode. For that reason letting the anode dissolve to nothing is not a good idea.
 
Feb 14, 2014
7,400
Hunter 430 Waveland, MS
Any issues with bonding the stanchions?
Normally no issues for galvanic current, but when you bond you life lines, you make them part of lightning protection. Mine are isolated from a nearby water strike and lets people hold on to them with out fear of a back flow of electricity.

I use a drop zinc when in transient marinas or when the diver can't be readily available.

Remember the zinc to shaft/prop is just one part of the galvanic "electrical circuit".
The other electrical connection is through the water.;)

The lower the water resistance, the more likely the drop zinc is working best.
Lower resistance is smaller distance, salty water, higher water temperatures and last...
Surface Area of the zinc exposed.

Your Prop Zinc is very close to the Prop shaft. Drop Zinc should be positioned as close to that as possible and Flat wide drop Zinc will normally take the lion's share of the sacrifice.:)
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Since my use is temporary, I use a cheap Auto jumper cable through a portal to connect to my engine shaft. Portal is in the Head, so rain is not an issue.
Jim...