Odd Anode deterioration

[jon and michie]

Hi - i had the boat hauled out on Monday in readiness for drive oil change and anti fouling.
What I have noticed is the ring Anode behind the props has deteriorated only on the starboard side.
Would this indicate that a electrical current has been coming from the starboard side???
Jon

 

[NorthUp]

I would investigate the port side, look for a bad electrical connection from anode to the drive.
How long do the anodes usually last?

 

[jon and michie]

The 1st season the whole ring had gone after 3 months.
2nd season I moved marina's and added an extra anode and the ring anode had survived although deteriorated after 8 months.
3rd season I added another extra anide to the drive and nearly 9 months - the ring had gone as i said earlier on the starboard side.
When I have installed all anodes I do check for continuity.
I am thinking it is a neighbouring boat with an electrical fault - as I sent a camera down after 5 months in the water and the deterioration was quite even all round.
Until the new neighbouring boat arrived.
I will post pictures tomorrow
Jon

 

[kashurst]

have you got a working galvanic isolator fitted?

 

[jon and michie]

I do have a working galvanic isolator which also has indicators if there is any electrical leakage from my boat
Jon

 

[superheat6k]

Check for DC leaks, notably through bilge pump float switches. Don't as me how I know this.

With everything turned off except essential service disconnect the +VE lead from the battery then measure voltage between the terminal and connector just removed. This should be 0 volts. Anything else then you need to find our why there is a current flow.

Anode wear bias is often caused by stray currents to the berthed to side. Finding and then resolving these - Good luck !!!

 

[A_8]

Do you have stainless steel props?

 

[bluetooth]

What model do you have? I've had more anode deterioration than usual this year

 

[bluetooth]

I have. Is this a known factor?

 

[jon and michie]

Check for DC leaks, notably through bilge pump float switches. Don't as me how I know this.

With everything turned off except essential service disconnect the +VE lead from the battery then measure voltage between the terminal and connector just removed. This should be 0 volts. Anything else then you need to find our why there is a current flow.

Anode wear bias is often caused by stray currents to the berthed to side. Finding and then resolving these - Good luck !!!

Thanks superheat6k - I have a galvanic isolator fitted which has ac and dc leak detection indicators.

 

[jon and michie]

Do you have stainless steel props?

Hi A8 - yes the boat has stainless props.
but as I have beefed up the anodes and moved marina there has been a considerable improvement over the last 3 seasons
jon

 

[jon and michie]

What model do you have? I've had more anode deterioration than usual this year

Hi Bluetooth - I am on a kad 300 with DP-G drives

jon

 

[jon and michie]

Right here is the leg after its first 3 months in the water back in 2016



the ring anode behind the prop was well worn down for 3 months use

Here is the picture of the leg after priming and before antifouling and anode went on - if you notice a hole on the left side fin this is where I added an extra anode for the 2nd season in 2017 which I had moved marinas by then



The ring anode at the end of 2017 was pretty much like the first picture but bear in mind that this time the boat had been in the water for 8 months.

Here is a picture at the beginning of this year with another addition anode fitted to the fin







These are the photos taken on Monday
The bar anode which looks in good shape for just under 9 months in the water



The additional anodes on the fin - Notice how the starboard is more worn down



Portside view of the ring anode which after 5 months I sent inspected with my camera hasn't changed much



Starboard side - totally shot



I know that the anodes are there to take electric hits in the water - but I find it odd how the anode has only gone on one side hence that is why I am thinking it is a neighbouring boat that has done this - which recently moved into the area

Thanks for the replies so far
jon

 

[BruceK]

My ring anodes wear very quickly like yours have shown. The remaining anodes are showing expected wear. I have SS props on too. What I noticed was when I put on ali props the wear was acceptable. I also found that the anode inside my SS props (part of the hub) wears very quickly after rehubbing the props. I am not sure whether you can replace these anodes or have to rehub. Either way mine haven't been rehubbed for 3 years and the original hub anodes has long since disintegrated. I have a sneaky suspicion it's this that accelerates the ring anode wear, but a £100 a pop each year for rehubbing (£400 total) I am happy to just beach the boat mid season just before the low water slack and quickly change the ring anode.

 

[superheat6k]

Thanks superheat6k - I have a galvanic isolator fitted which has ac and dc leak detection indicators.

Don't rely on the GI indicators for this problem - these will only light up if they detect current flow through the GI itself.

Your idea this might be due to a neighbouring boat could be correct. I would suggest a dangling anode positioned 1-2' from the area you are seeing heavy anode wear, but this must be electrically connected to the leg. You can make a dangling anode from a couple of old part worn anodes bolted to a stainless leader cable rising out of the water before using conventional copper cable above the water to complete the circuit. An extra piece of rope tied from the dangling anode to the throttles will remind you it is hanging before you start the engines.

Electrolytic, Galvanic and Stray current corrosion is an incredibly complex problem to understand and resolve. I can send you some links to good books (PDFs) on the subject. Just PM me. Often there will be more than one cause - my last boat had four or five issues to resolve before I finally sorted the problem.

 

[jon and michie]

Thank you superheat6k - - I have just made a hanging anode using my old anodes.
I just find it odd as it is not an exact science but also not un this case even wear
Jon

 

[BruceK]

Why would you expect even wear? Where in nature have you ever seen anything even?

 

[A_8]

Hi A8 - yes the boat has stainless props.
but as I have beefed up the anodes and moved marina there has been a considerable improvement over the last 3 seasons
jon

Ok, I had the same on mine and the SS props are specced to be electrically isolated from the rest of the drive which happens between the hub and the prop, there are some plastics that goes between the cone and the prop as well to keep it isolated.
Over time stuff gets in there and creates a connection or for me the prop repair man did not understand this so after the refurb I got the same on one of them.
If this is your problem there is an easy test and that is to ohm meter between the hub and prop and sometimes it will help cleaning around the hub and making sure the ring sitting there don't touch the prop. With the props on the drive you can easure between the drive and the prop blades.
Interestingly I did the same as you beefing up with lots of anodes and after a few years I learned about this, fixed the props and suddenly the anodes lasted a lot longer.

 

[bluetooth]

Sorry I meant what type of isolator ? (did reply from phone so pressed wrong reply button)
What are and have people used to plug into shore power ?

I have already set up some old anodes to dangle off stern and like the idea of extra anodes.
Really helpful thread.
Many thanks all

Hi Bluetooth - I am on a kad 300 with DP-G drives
jon

 

[BruceK]

Ok, I had the same on mine and the SS props are specced to be electrically isolated from the rest of the drive which happens between the hub and the prop, there are some plastics that goes between the cone and the prop as well to keep it isolated.
Over time stuff gets in there and creates a connection or for me the prop repair man did not understand this so after the refurb I got the same on one of them.
If this is your problem there is an easy test and that is to ohm meter between the hub and prop and sometimes it will help cleaning around the hub and making sure the ring sitting there don't touch the prop. With the props on the drive you can easure between the drive and the prop blades.
Interestingly I did the same as you beefing up with lots of anodes and after a few years I learned about this, fixed the props and suddenly the anodes lasted a lot longer.

yes. This is my experience too.