Moorers beware

[manxmike]

Moored in a Marina but not using the mains power? Don't imagine for a minute that you are not at risk of galvanic reaction from other people's boats!

I was horrified to discover that despite not using the mains supply for more than a few minutes every month, my hull had developed serious pitting causing the value of the boat to sink without trace. The buyer's surveyor said that the hull needed overplating urgently at a cost of some £8,000 to £10,000.

The only cause of the reaction I can think of is being bracketed on the Marina by live-aboard boats plugged in permanently to the mains power and possibly not having a galvanic isolator fitted, thus causing the problem with my hull.

When last examined (four years ago) the pitting was minimal and the hull was sound - now it is down to 2 to 3mm in places.

Sadly I had to cut my losses and accept a seriously low price for the boat. There was no way I could afford to have the overplating done. I had hoped to raise sufficient to make the first few payments on a new Sailaway hull, but those plans have now gone on hold for the foreseeable future.

Ah well, we learn from our mistakes and oversights. Maybe I should have gone for a GRP hull instead.

[cuthound]

Did you have a galvanic isolator (GI) or isolation transformer (IT) fitted?

Of not, any difference in the earth potential between your boat, and any other boat, metal piling or the landlines earth connection will cause a small current to to flow between the two and cause galvanic corronion. 

Even if you have a GI or IT it should be regularly checked for correct operation to ensure your safety and in the case of the GI to ensure the hull is still protected against stray currents. 

Edited November 5, 2017 by cuthound
Spillung

[manxmike]

Sadly I had neither fitted - not using mains power (except on very rare occasions) I didn't think I needed either. Expensive way of learning the error of my ways!

[OldGoat]

It's the earth connection what dun it yr' Honour and not whether you had used any 'leccy as you have sadly discovered.

I'm guessing - but if all the other boats had GIs fitted you might not have suffered any corrosion

[nicknorman]

When you say “not using shore power” do you mean it wasn’t plugged in, or it was plugged in but switched off?

If the former, a GI or IT isnt going to help. But it does seem odd - somehow there must be an electric field set up by one or both other boats.

if the latter, it doesn’t matter whether the shore power is switched on or not, it is the presence of the earth connection that is the issue causing galvanic corrosion, and why you need a GI or IT.

[manxmike]

3 minutes ago, OldGoat said:

It's the earth connection what dun it yr' Honour and not whether you had used any 'leccy as you have sadly discovered.

I'm guessing - but if all the other boats had GIs fitted you might not have suffered any corrosion

That was the direction my thoughts were going in. 

Nicknorman - not plugged in at all, rubber fenders between myself and the metal walkway. Maybe I should have earthed the hull to something?

[mrsmelly]

This is a sad and frightening post. I am about to winter in one of these plugged in marina places. My boat is proper and has a thingy isolater jobby. How do I check its working? Is there a way a lectrical bod can ensure its ok?

[manxmike]

Sorry to scare you Tim, but if someone can profit from my experience or at least avoid the same pitfall, then it hasn't been a totally dreadful period, just a new section of life's learning curve.

I'm doing my swan thing - calm exterior, but it's all happening under the surface!

[Naughty Cal]

Don't think GRP boats are immune. They still have metal bits below the waterline that need protecting. Usually expensive metal bits at that.

 

[GUMPY]

Which marina? Not in Nantwich is it?

[manxmike]

No, not in Nantwich, just outside at Choldmonston, why?

[OldGoat]

31 minutes ago, manxmike said:

That was the direction my thoughts were going in. 

Nicknorman - not plugged in at all, rubber fenders between myself and the metal walkway. Maybe I should have earthed the hull to something?

If you've had no electrical capable connection twixt yourself and the shore, then you can't blame the liveaboards - 'leccywise. But you might have a 'case' if they're contributing to increased acidity (canals are relatively acid anyway) by tipping overboard what they shouldn't and ditto what you're all allowed to do anyway.

I wonder what state your anodes are / were in? If shot then lack of that sort of galvanic protection might be the net cause of your disaster 

 

30 minutes ago, mrsmelly said:

This is a sad and frightening post. I am about to winter in one of these plugged in marina places. My boat is proper and has a thingy isolater jobby. How do I check its working? Is there a way a lectrical bod can ensure its ok?

Horrified me a bit as well. I've - this year  moved from a delightful island (but with rubbish access) with mega litres of freshwater rushing past, into a posh new marina extension with 'leccy everywhere. I haven't yet fitted a GI (still in its box - a lorra use...)

Ignore these two lines What you need to do is to measure (with the mains switched off) the DC voltage between the shore side of your GI and the boat side There are only two terminals on the GI so difficult to get it wrong. Use CS's method below

Wear rubber gloves.

There's no magic, so not a problem to a man of your calibre. Have a look  at Sterling's website where Charles senior has written an article on the subject.

Edit: Go here -

https://sterling-power.com/pages/instruction-manuals

download the manual for Pro-Save A&C and follow the section for testing. He suggests disconnecting the mains and testing the diodes for a short circuit. Much safer that measuring the voltage (if any) between the two earth cables  

Edited November 5, 2017 by OldGoat
Delete my poor suggestion...

[manxmike]

5 minutes ago, OldGoat said:

wonder what state your anodes are / were in? If shot then lack of that sort of galvanic protection might be the net cause of your disaster 

Probably on the way out to be honest. They were new four years ago, and visually they seemed to be still there. Without having the boat out of the water (£400) it is difficult to say for sure.

I did wonder about phasing between the boats bracketing mine, it doesn't take much to set up a field.

 

I've stopped changing my Avatar now - honest I have!

Edited November 5, 2017 by manxmike
Indecision

[Keeping Up]

If the boat wasn't plugged in then neither GI nor isolating transformer could have been used. It sounds unlikely to have been caused by mains electricity. Perhaps it was a completely different cause? My boat suffered from similar corrosion problems last year, resulting in the need for a complete overplating, but it wasn't in a marina. Although it was plugged into the mains it was correctly protected by a GI and it is worth noting that the 3 other boats that use the same supply had no problems. The latest thinking is that it may have been caused not by mains but by the 12 volt system. When a new engine was fitted after 23 years the new exhaust system provided a very good alternative connection between the engine and hull, which acting in parallel with the existing bond from hull to battery negative, caused up to 15 amps of the domestic charging current to choose the alternative path through the hull. After a year we will soon be having the (overplated) boat docked to see if the problem is now cured.

[cuthound]

Below are Instructions on how to test a GI. I usee the digital multi-meter diode test method.

Note that some GI's use only a single diode in each direction, so give lower reading some friends 0.9 - 1.0 volts.

Edited November 5, 2017 by cuthound
Clarification

[GUMPY]

31 minutes ago, manxmike said:

No, not in Nantwich, just outside at Choldmonston, why?

There were similar happenings in a marina up that way. 

[manxmike]

Just now, Loddon said:

There were similar happenings in a marina up that way.

Interesting, wish I'd known this sort of thing a while ago!

[Tim Lewis]

16 hours ago, manxmike said:

Probably on the way out to be honest. They were new four years ago, and visually they seemed to be still there. Without having the boat out of the water (£400) it is difficult to say for sure.

I did wonder about phasing between the boats bracketing mine, it doesn't take much to set up a field.

 

I've stopped changing my Avatar now - honest I have!

Scuse ignorance but if you have not had the boat out of the water to be able to check the anodes how was the survey carried out?

Tim

[manxmike]

The people who were intending to buy the boat had the boat dry-docked and a survey done - they then decided not to buy as a result of the survey.

[Machpoint005]

I wonder if they were the right type of sacrificial anode, and whether there was a sufficient number of them?

[manxmike]

Four anodes and absolutely standard - supplied and fitted by the Marina, not just to my boat but to most boats they service

 

[Sea Dog]

9 hours ago, manxmike said:

The people who were intending to buy the boat had the boat dry-docked and a survey done - they then decided not to buy as a result of the survey.

Then I'd suggest, before you do anything drastic, you get your own survey by another surveyor that you can trust. At the moment it sounds like you don't really know what you're dealing with. I hope it's not as bad as you currently fear.

[manxmike]

To be honest I decided to bite the bullet. Apart from the pitting - which I have no reason to doubt - all the windows need replacing, the batteries are due for replacement (five years old and not holding charge as well as they used to), plus various other work needed.

In the cold light of serious reason the boat was reaching (had reached) a point where it was becoming a money pit, 30 years old with a 6mm base plate and 5mm sides. Without extensive funds to throw at it, which would have equated to buying a much newer boat or even a new build sailaway it was an unrealistic proposition. OK, I've lost money on the sale, but I've also saved myself the mooring fees, licence, insurance and the ongoing expenses.

My family have had four years of great fun, three generations have enjoyed the time we have spent aboard - that's something that can't be quantified in terms of money.

Someone has now bought a boat that, with time and money, could well see another 30 years of service. I simply do not have the finances to fund the sort of work needed at the moment.

Realism can be uncomfortable, but it does shine a light into the dark corners we would all rather ignore.

[Sea Dog]

I missed that you'd now sold her Mike. Glad you and your family enjoyed your time afloat and you're leaving with happy memories.

Edited November 7, 2017 by Sea Dog
Sp

[manxmike]

Determination to get back on the canals has brought to the surface a number of thoughts.

1. Buy a share in a boat

2. Hire

3. Buy a GRP boat in need of tlc

To be honest the option I am favouring is number 3. Reasonable GRP boats can be bought for well under £10,000, obviously in need of some work but that's not a problem. There are several advantages I can think of - cheaper licence and mooring, somewhat lower running costs, much less room for swmbo to fill with "things we can't live without". I do not intend to live aboard and the majority of use would be during the "summer" months (April to October).

If anyone has other options I would love to hear them.

That splashing sound is me trying to get the bathtub to float!