Electrolysis at Marinas?

[maby]

I don't suppose every boat or marina power point has an installed circuit breaker but surely the majority do? An electrician friend tests them by touching the bare ends of wires to ensure the breaker trips, indicating to me that a relatively high resistance short will cause one to open. So I'm not too sure about your 'electrical fault injecting current into the network'.

Well, I'm not convinced that it is a particularly common problem, but I maintain that the cell effect of linking multiple boat earths without an electrical fault anywhere is far less plausible an issue - we all have anodes installed - the anodes on your neighbour's boat are far better bonded to his propshaft or sterndrive than they are to yours, ten or fifteen feet away - the additional demands on your anodes are going to be small.

Anyway, it would not be the circuit breaker that is the protection, it's the earth leakage RCD. I don't know how sensitive they are - just a few milliamps leakage could have quite a bit effect on your anodes.

 

[BruceDanforth]

I don't have anodes installed.

Well, I'm not convinced that it is a particularly common problem, but I maintain that the cell effect of linking multiple boat earths without an electrical fault anywhere is far less plausible an issue - we all have anodes installed - the anodes on your neighbour's boat are far better bonded to his propshaft or sterndrive than they are to yours, ten or fifteen feet away - the additional demands on your anodes are going to be small.

Anyway, it would not be the circuit breaker that is the protection, it's the earth leakage RCD. I don't know how sensitive they are - just a few milliamps leakage could have quite a bit effect on your anodes.

 

[Daydream believer]

To reduce your exposure, connect any electrical equipment directly to shore power rather than through the boat electrics, especially if leaving connected for any length of time.

But most boat electrics are 12 or 24V-- or am i missing something here??

 

[Andrew G]

Lusty, not all marinas are the same. In mine there are no live-aboards and you need "Club Approval" to stay on board even for a shortish period (it is mostly racing boats with mains leads charging batteries before the next race - no solar panels no wind generators etc). I am not suggesting unplugging peoples leads but I am suggesting that the club promulgate its existing rules which then helps me have a conversation with my neighbours (whom I've only just met see PS below).

My interest in the OP's question is how many neighbours do I have to talk to (there are 250+ boats)?
I am not an expert in this field so I am having a problem with the concept that a fault on somone else's boat (or club infrastructure) could damage or sink my boat - and that I should not do anything reasonable to stop it? Any suggestions as to how I can prevent damage would be appreciated. Cheers, Andrew

Edit: I should add that my power lead is not connected to my boat but only to the item in use (kettle, drill, charger etc) and never when I'm not onboard (lead gets coiled up and stowed below). It is a brand new marina so every power outlet has Earth Leakage Protection. Andrew

 

[maby]

Lusty, not all marinas are the same. In mine there are no live-aboards and you need "Club Approval" to stay on board even for a shortish period (it is mostly racing boats with mains leads charging batteries before the next race - no solar panels no wind generators etc). I am not suggesting unplugging peoples leads but I am suggesting that the club promulgate its existing rules which then helps me have a conversation with my neighbours (whom I've only just met see PS below).

My interest in the OP's question is how many neighbours do I have to talk to (there are 250+ boats)?
I am not an expert in this field so I am having a problem with the concept that a fault on somone else's boat (or club infrastructure) could damage or sink my boat - and that I should not do anything reasonable to stop it? Any suggestions as to how I can prevent damage would be appreciated. Cheers, Andrew

Edit: I should add that my power lead is not connected to my boat but only to the item in use (kettle, drill, charger etc) and never when I'm not onboard (lead gets coiled up and stowed below). It is a brand new marina so every power outlet has Earth Leakage Protection. Andrew

I think you are pretty much immune. Nothing the other boats do can impact on yours unless there is a connection between the shore power earth and the metal components of your boat that are in the water.

 

[lustyd]

It’s against our marina rules to leave a mains lead connected when unattended - but it is not policed (I’m working on it). I have purchased a “Galvatest” (at vast expense) but by dangling it over the side I get a reading of any stray currents nearby – so far so good.

Lusty, not all marinas are the same. In mine there are no live-aboards and you need "Club Approval" to stay on board even for a shortish period (it is mostly racing boats with mains leads charging batteries before the next race - no solar panels no wind generators etc). I am not suggesting unplugging peoples leads but I am suggesting that the club promulgate its existing rules which then helps me have a conversation with my neighbours (whom I've only just met see PS below).

I'm having trouble reconciling these two statements, you say the marina isn't used that way yet you want to start policing those who are using it that way. It seems to me that your neighbours use the marina like a normal marina and you don't like it. Most marinas have rules which everybody ignores, pretty much all have rules against live-aboards yet most marinas do have them. As others have said, if you've not plugged your boat in to the earth (or connected direct to their boat with jump leads!) then it's unlikely those other boats are giving you trouble so live and let live

 

[terry.mcneill]

I've just had very expensive experience with galvanic corrosion.

Boat Westerly Oceanquest with sail drive (aluminium) and with anodes on the hull and a ring anode at the saildrive/prop interface, both newly fitted in April.
In September I find emulsified oil in the saildrive. Upon lifting out to investigate, I find the saildrive is like Swiss cheese. Riddled with deep penetrating corrosive holes. Ring anode virtually non-existent. Sail drive and anodes replaced again (ouch!). And all bonding connections in the boat checked.
I NEVER leave shore power on when not aboard. Nearest boat last season was a steel hull live-aboard (so im guessing drawing shore power pretty continuously).
Both of us are scheduled to occupy the same berths this year. Should I be concerned? Or were my problems likely unconnected (figuratively and literally) with nearby boats?

 

[vyv_cox]

Many people report extremely short anode life on saildrives, even to the extent that they need to replace them part way through a season. Without studying the precise details I would find it difficult to advise. I'm a little concerned to read that you 'checked all bonding connections'. Most saildrives I am aware of are isolated from everything else aboard. Bonding of below water metal fittings is not recommended nowadays, partly because of exactly the problems you are experiencing.

 

[terry.mcneill]

Many people report extremely short anode life on saildrives, even to the extent that they need to replace them part way through a season. Without studying the precise details I would find it difficult to advise. I'm a little concerned to read that you 'checked all bonding connections'. Most saildrives I am aware of are isolated from everything else aboard. Bonding of below water metal fittings is not recommended nowadays, partly because of exactly the problems you are experiencing.

I meant the connections inside the boat from the hull anode to the engine etc - not the saildrive which is a whole different set-up. In any event the work was done by the marina engineer, not by me.

 

[Tranona]

I meant the connections inside the boat from the hull anode to the engine etc - not the saildrive which is a whole different set-up. In any event the work was done by the marina engineer, not by me.

Think you need to look at that more closely. There is no need for a hull anode connected to the engine as there is nothing in the engine to be protected. Most saildrives are electrically isolated from the engine specifically to avoid any galvanic action between the engine and the drive. The drive casing is then protected by the anode. It is feasible to increase the amount of anodic protection for the drive by connecting an additional anode to the drive casing (not the engine) and this is commonly using a hanging anode when moored. Saildrive anodes can last a long time, but it seems to vary from boat to boat and location to location. When my boat was in the Med the anode lasted 4 years or so, but much less now that it is in the UK.

It is possible that your hull anode to be connected to skin fittings, but as Vyv says this is not normally recommended as skin fittings, seacocks etc are not normally connected to anything else so do not suffer from galvanic corrosion.

 

[terry.mcneill]

Interesting. Theres no anode on the actual saildrive leg, just the ring anode at the prop. Should there be one on the leg? She's not in the water yet, so still time to fit one.....

 

[maby]

Interesting. Theres no anode on the actual saildrive leg, just the ring anode at the prop. Should there be one on the leg? She's not in the water yet, so still time to fit one.....

The ring anode is bolted to the sail-drive, not the prop, isn't it? That's all most Yanmar saildrives have.

 

[vyv_cox]

In any event the work was done by the marina engineer, not by me.

Several people have been reporting to me through my website that their 'marina engineers' are recommending outdated and unsafe practices in many areas, especially where bonding, anodes and suchlike are concerned. I suggest you check exactly what is being proposed and verify elsewhere before agreeing.

 

[Tranona]

Interesting. Theres no anode on the actual saildrive leg, just the ring anode at the prop. Should there be one on the leg? She's not in the water yet, so still time to fit one.....

Yes, there is a ring anode on the leg behind the prop, but is not connected to the prop. Pretty obvious visually if it is not there! On older Volvos and Yanmars it is a one piece ring bolted to the saildrive housing and the prop needs to come off to change it. Newer Volvo drives (post 2006) have a bigger two piece anode that clamps to a bracket behind the prop and is easier to change. The standard prop is aluminium and is electrically isolated from the drive by a rubber bush in the centre so does not need an anode. However, if you have a folding or feathering prop they often are made of mixed metals and have their own anodes, either button type or cones on the end of the prop boss.

 

[BrianH]

Many years ago a new neighbour boat arrived next to me; it was in an extremely decrepit condition and its owner somewhat antisocial in many ways. We were both stern-to in boxes in my Italian marina that proscribes shore power connection when no one is aboard. Of course, that is difficult to control but the patrolling marinaros would switch off the power to any cable where it was clear the boat was unattended. My neighbour, who lived locally and came and went frequently, left his cable permanently plugged in and powered; more times than not it went unnoticed. My boat at that time was a fin-keeled Trapper 500 with the keel base section being of iron, keel-bolted through the GRP stub to thick layup floors in the bilge. I never left shore power on when not aboard. When it was on, the 220V supply had no other connections other than direct to the appliance being used - heater or two-ring hob. The supply was not metered.

The next Spring I hauled out for anti-fouling and was surprised to see the paint on my iron keel flaked away in blotches and the iron itself extensively and deeply pitted - but only on the side that was next to my shabby neighbour, the other was absolutely unscathed, clean metal under the old anti-fouling. The damaged keel side was only a metre or two from my neighbour's hull. The zinc anodes were not unusually depleted but changed as normal.

By the time I relaunched my neighbour had moved on to a berth on another pier and I never had a repeat of the problem. I have always wondered if he was responsible - but could never understand how.

 

[savageseadog]

I've been in the same marina with two different yachts, both with saildrives and folding bronze props. I had two Gori props corrode away in the space of two years each on one boat and no problems at all on the other. It could have been charging arrangements, stray currents, other boats nearby, poor mains earthing or the underwater arrangements of the yachts, I know not what. I'm an electrical/electronics engineer and I can honestly say it's a very difficult issue to predict, measure and/or do anything about.

 

[VicS]

I've just had very expensive experience with galvanic corrosion.

Boat Westerly Oceanquest with sail drive (aluminium) and with anodes on the hull and a ring anode at the saildrive/prop interface, both newly fitted in April.
In September I find emulsified oil in the saildrive. Upon lifting out to investigate, I find the saildrive is like Swiss cheese. Riddled with deep penetrating corrosive holes. Ring anode virtually non-existent. Sail drive and anodes replaced again (ouch!). And all bonding connections in the boat checked.
I NEVER leave shore power on when not aboard. Nearest boat last season was a steel hull live-aboard (so im guessing drawing shore power pretty continuously).
Both of us are scheduled to occupy the same berths this year. Should I be concerned? Or were my problems likely unconnected (figuratively and literally) with nearby boats?

Your problem sounds very similar to Nigel Mercier's experience.

What engine do you have.

He has a VP in which he believed that the saildrive was isolated from the engine....... but this is not so. The engine instead has an isolated negative return ... So rather than the saildrive being isolated from the engine the whole darned lot is isolated from battery negative. HOWEVER He had a short between the starter motor negative and the engine block. IIRC his keel is connected to battery negative. He therefore had a galvanic corrosion cell consisting of his keel and his saildrive leg since the two where effectively connected via the DC negative and the short on the starter motor ....... the sail drive leg lost the electrochemical battle with the keel.

Tell us what engine and when Nigel joins the discussion he will be able to elaborate, correct any errors in my account and maybe give you something to investigate if the same could apply.