Zincs corroding too fast.

[Charles Erwin]

Measure the shaft, motor cooling water intake, motor block.

You have a value .210 volts at what you call "bonding wire." You say it starts at the keel bolt. Where does go from there and where does it eventually end? Do you know if there is a zinc bolted to the keel on the outside?

Are any of the items on the list (apart from the keel) connected by a wire? This is usually a green wire that goes from item to item and ends at the motor block or an external zinc thus the items are said to be "bonded." )

I assume the items you measured are not submerged in bilge salt water - which could connect them together intermittently. If no bilge water submersion then - so far

The values suggest the through hulls are high quality bronze, the items are not bonded, the items are not exposed to DC current, and the items are not players in zinc loss because they are not connected to the zincs that are wasting.

The motor/shaft/cooling water intake are connected to the wasting zincs and these measurements will be the most helpful. Record the results with shore power cord plugged in and shore power unplugged. Also with battery cable connected and not connected - that includes house and start batteries.

Charles

 

[joyof10]

I'll be back on the boat on Tuesday and will measure the other items you have mentioned. I assumed, perhaps incorrectly, that because the bonding wire connected all of those things that I could measure them all at one location. I'll report back once I have the data. Thanks.

Measure the shaft, motor cooling water intake, motor block.

You have a value .210 volts at what you call "bonding wire." You say it starts at the keel bolt. Where does go from there and where does it eventually end? Do you know if there is a zinc bolted to the keel on the outside?

Are any of the items on the list (apart from the keel) connected by a wire? This is usually a green wire that goes from item to item and ends at the motor block or an external zinc thus the items are said to be "bonded." )

I assume the items you measured are not submerged in bilge salt water - which could connect them together intermittently. If no bilge water submersion then - so far

The values suggest the through hulls are high quality bronze, the items are not bonded, the items are not exposed to DC current, and the items are not players in zinc loss because they are not connected to the zincs that are wasting.

The motor/shaft/cooling water intake are connected to the wasting zincs and these measurements will be the most helpful. Record the results with shore power cord plugged in and shore power unplugged. Also with battery cable connected and not connected - that includes house and start batteries.

Charles

 

[Charles Erwin]

I am a little confused on one point. You said

I assumed, perhaps incorrectly, that because the bonding wire connected all of those things that I could measure them all at one location.

If a wire connected each item on the list - one to the next as you say - then voltages you measured would all be the same at every one of the items you measured. However, your measurements show each item is at a different voltage. That means these items are not wired one to the next, nor to the keel bolt.

Please clarify.

Charles

 

[Maine Sail]

I am a little confused on one point. You said



If a wire connected each item on the list - one to the next as you say - then voltages you measured would all be the same at every one of the items you measured.

Bingo, that is what bonding is supposed to do..

However, your measurements show each item is at a different voltage. That means these items are not wired one to the next, nor to the keel bolt.

Please clarify.

Charles

They may look bonded but be could also be so corroded as to be of no electrical value. I have seen this a number of times. For every seacock to be at a different potential would indeed be odd though... Usually one or two have lost bonding continuity while others are still technically making a connection and will be at the same potential. These seem to all be different....

 

[smokey73]

Charles (or Mainsail) I could not find the pdf attachment that gave the instructions/diagram for checking hull potential and potential at the various locations. My Hunter 40.5 is also wasting zincs too fast (about 50% in two months) so I need to track down the issue and would appreciate any help. Thanks in advance

 

[Charles Erwin]

At #5 above. If not try again at the attachment.

 

[joyof10]

The through hulls were not connected to any bonding wire. Only the standing rigging and the items in the engine room. That is why I didn't measure the engine, etc. since I thought it would be the same as what I measured at the keel bolts.

I am a little confused on one point. You said



If a wire connected each item on the list - one to the next as you say - then voltages you measured would all be the same at every one of the items you measured. However, your measurements show each item is at a different voltage. That means these items are not wired one to the next, nor to the keel bolt.

Please clarify.

Charles

 

[GWG]

Simple fix

I had zinc issues with 2 Beneteaus, both with Autoprop--which has a small zinc. Simple solution is to ground the stern rail to the engine and hang a zinc off the stern rail.There are several types of zincs that can be connected to the rail with an alligator style clip. Just remember to pick it up when you go sailing.

 

[joyof10]

My 343 has the stock prop with standard sized zincs. Rather than a work-around, I'd really like to get to the bottom of what is causing the problem and resolve the issue once and for all. I'll be taking more measurements today.

I had zinc issues with 2 Beneteaus, both with Autoprop--which has a small zinc. Simple solution is to ground the stern rail to the engine and hang a zinc off the stern rail.There are several types of zincs that can be connected to the rail with an alligator style clip. Just remember to pick it up when you go sailing.

 

[Donnybrook]

See Main Sail's post #19. If your AC ground is connected to your DC ground and you don't have a GI or IT, you will rapidly go thru zincs. That simple. You can disconnect that link and be like 80% of boats around you or install a GI or IT.

 

[Charles Erwin]

We cannot tell if there is a galvanic threat from off-the-boat metal objects quite yet.

We will probably learn if there is vampire galvanic activity from a "more noble" neighbor or from submerged marina metals because Joyof10 will measure the potential of the shaft/propeller/zinc assembly - shore power cable plugged in and also unplugged.

Charles

 

[Gunni]

That isn't a bonding wire, it is an attempt to ground your rig. Beneteau doesn't do bonding.

 

[joyof10]

I have done as suggested and I think we have located the root of the problem.
None of the through hulls has a grounding wire (what I was calling a bonding wire). All of the through hulls measured between .69 to .98 with the galley sink drain being the highest. This includes the measurements from the stern tube inlet and the engine water inlet. None of these measurements changed, regardless of whether shore power was hooked up, or whether any of the batteries or common ground were switched on. Someone earlier in the thread suggested that the measurements for the through-hulls simply meant a good quality bronze fitting. Works for me.

Now to the interesting part. The engine, the prop shaft and the bonding (ground wire) at the fuel tank which are all connected by a green wire, all measured .14 when the shore power was attached and switched on, but went to 0.0 when the shore power was disconnected. I think that this must be the culprit.

I have ordered a galvanic isolator from West Marine which I will be picking up on Thursday. I am hopeful that this is the solution. I know that was suggested early on in the thread, but I learned from the experience of taking all of the measurements.

Any other comments are welcome. Thanks to all for your suggestions and assistance. If this doesn't solve the problem, I will certainly be back.

We cannot tell if there is a galvanic threat from off-the-boat metal objects quite yet.

We will probably learn if there is vampire galvanic activity from a "more noble" neighbor or from submerged marina metals because Joyof10 will measure the potential of the shaft/propeller/zinc assembly - shore power cable plugged in and also unplugged.

Charles

 

[joyof10]

Good news (I hope).
I installed the Galvanic Isolator today and then retested the shaft with the shore power hooked up and on. The reading was 0.0.
Now the real test will be whether my zincs last longer.
Thanks again to all who replied with suggestions.

 

[Maine Sail]

Good news (I hope).
I installed the Galvanic Isolator today and then retested the shaft with the shore power hooked up and on. The reading was 0.0.
Now the real test will be whether my zincs last longer.
Thanks again to all who replied with suggestions.

Now you see what GI's do. You were protecting boats other than yours with your zincs, now you are not..

 

[joyof10]

Right you are.

Now you see what GI's do. You were protecting boats other than yours with your zincs, now you are not..

 

[PDReynolds]

Folks,
I also have a similar rapid erosion of my zinc. My 2006 Beneteau has only the little zinc on the end of the Max Prop. My plan in the spring is to install a new shaft zinc, replace the one on the end of the prop and also drill a hole through the training edge of my iron keep to fit a couple more big zics.

After reading this post, I am thinking that my source of galvanic action might me coming from my own boat. I have about .5 volts DC potential from my boat to the water even if my 30 amp power cords are disconnected. Another note about this, my iron keel has quite a bit of rust that needs to be redone now that y boat is on the hard for the winter.

What is the typical process to determine any possible causes for an internal DC leak?

 

[Bloodline]

Boatzincs.com. Part number bd-##. Bd-30= 30mm shaft. Slim zinc collars that fit in front of bene props.