Marine Electrictian- Hamble

[olly_love]

The rapid loss is in the button anodes on the leg and is at such a rate so as to suggest electrolytic loss as opposed to galvanic. I would suggest that a little previous pitting on the prop may or may not be a factor in the present issue and if the prop is ( truly) isolated from the leg and the buttons then focusing on the prop is a bit of a red herring. All of course if I've got the drift of the previous posts, if not then I'm just jibbering so please ignore me...?
The enquiry about the previous VHF was that some brands ( icom being one) connect the RF ground to battery negative where as the more commercial brands tend not too and so a change in set can when active present a connection to battery negative to anything connected to the ariel ie masts ect.

Thats intersting as Icom ( the new VHF) have said they its not needed to Ground! via the alternative stud

 

[Tranona]

Are you sure? post #4 says "Isolated from the leg anode" in post #9 I do ask if it is isolated from the drive as well. Neither do we know what is, or isn't relevant. We just don't have the information to make definitive statements. not trying to be clever or knock your post just as I see it. As with many of these technical posts on site investigation is the only real answer. Good point about Darglow!

As the ring anode on the leg is bolted to the leg and is clearly electrically bonded as it is working then there is no electrical connection to the drive and therefore anything in the 12v circuit. If the boat is in a ,marina then it could be stray currents causing electrolitic action but this is notoriously difficult to trace. I have difficulty in understanding how one can establish that the wear on the prop anode is only occurring when the prop is spinning.

 

[olly_love]

The boat was unused for a month and new annodes were put on prior to motoring to and from Dartmouth, on return the prop annodes had 95% gone in the matter of 200 miles and 4 days ( I dove the boat after to check)

 

[Alex_Blackwood]

As the ring anode on the leg is bolted to the leg and is clearly electrically bonded as it is working then there is no electrical connection to the drive and therefore anything in the 12v circuit. If the boat is in a ,marina then it could be stray currents causing electrolitic action but this is notoriously difficult to trace. I have difficulty in understanding how one can establish that the wear on the prop anode is only occurring when the prop is spinning.

Yes the ring anode is as you say, and is, from the readings taken, isolated from the prop. However, that is not the drive shaft. Only the leg.
We of course cannot verify this here, so perhaps, hang fire on that.

I concur with your other comments. The scenario has now changed slightly as Olly now says that he motored all the way to and from Dartmouth. We therefore have no proof that the anodes would not have suffered the same under sail. We don't know that it is only happening with the engine running. I am still inclined to think that he has something onboard that is causing stray currents. Ean_p may have hit the nail on the head!
As you correctly say difficult to trace. I did initially suggest that he may need specialist expertise in the way of Cathodic protection. Possibly still applies.
Edit: Would be interesting to know how long was spent in Dartmouth and where moored?
it is also noted that this must have occurred prior to fitting the new alternator and since fitting the new prop. Did it occur with the old prop?

 

[Boater Sam]

The alternator change could be relevant. Was the original isolated negative?
Pardon my ignorance but how can the prop be isolated from the drive? Is it not a metal drive shaft?

 

[olly_love]

The alternator change could be relevant. Was the original isolated negative?
Pardon my ignorance but how can the prop be isolated from the drive? Is it not a metal drive shaft?

We had no change in the problem after changing the alternator over,

 

[olly_love]

Yes the ring anode is as you say, and is, from the readings taken, isolated from the prop. However, that is not the drive shaft. Only the leg.
We of course cannot verify this here, so perhaps, hang fire on that.

I concur with your other comments. The scenario has now changed slightly as Olly now says that he motored all the way to and from Dartmouth. We therefore have no proof that the anodes would not have suffered the same under sail. We don't know that it is only happening with the engine running. I am still inclined to think that he has something onboard that is causing stray currents. Ean_p may have hit the nail on the head!
As you correctly say difficult to trace. I did initially suggest that he may need specialist expertise in the way of Cathodic protection. Possibly still applies.
Edit: Would be interesting to know how long was spent in Dartmouth and where moored?
it is also noted that this must have occurred prior to fitting the new alternator and since fitting the new prop. Did it occur with the old prop?

Its 100% not when moored, we do not have any 240V or bilge pumps onboard and all electronics are isolated when the switch is off.

We were only in Dartmouth for 4 days and have had this issue for the past 18 months now,

The new alternator was 12 months ago and problem for 18 months now unfortunately.!

 

[superheat6k]

I stand by my advice to firstly clean and descale everything and assemble without grease as per the specific advice in the flexofold instructions. Do not yet disconnect the VHF. Then if the problem persists try disconnecting the VHF then. When following a diagnosis path introducing two actions will likely confuse the path and final conclusions you are seeking.

 

[VicS]

The rapid loss is in the button anodes on the leg and is at such a rate so as to suggest electrolytic loss as opposed to galvanic. I would suggest that a little previous pitting on the prop may or may not be a factor in the present issue and if the prop is ( truly) isolated from the leg and the buttons then focusing on the prop is a bit of a red herring. All of course if I've got the drift of the previous posts, if not then I'm just jibbering so please ignore me...?
The enquiry about the previous VHF was that some brands ( icom being one) connect the RF ground to battery negative where as the more commercial brands tend not too and so a change in set can when active present a connection to battery negative to anything connected to the ariel ie masts ect.

The button anodes are go the prop , not on the leg.

 

[ean_p]

The button anodes are go the prop , not on the leg.

View attachment 149099

Ah ! Well that'll be me just jibbering then......!

 

[Alex_Blackwood]

I stand by my advice to firstly clean and descale everything and assemble without grease as per the specific advice in the flexofold instructions. Do not yet disconnect the VHF. Then if the problem persists try disconnecting the VHF then. When following a diagnosis path introducing two actions will likely confuse the path and final conclusions you are seeking.

Agree, I think we have just about exhausted this as far as the forum goes. Local action required. I note that no one has recommended a local Electrician as originally asked for! Would be interesting to know if prop change was Like for Like?
Perhaps Olly can update on any progress.