Isuzu Trooper Owners Club UK™

[Paul V]

Wookie..I thought you worked on a rig in the Nth Sea..? Sorry to bring my question to the forum but it's amazing who is out there on the Web and who can direct you to the answers you are looking for..As a matter of interest the boat is based in Auckland New Zealand on the sunny Waitamata Harbour ..very salty..once home of the America's Cup..


Cheers for your patience and info..
PV

[Google]

[Paul V]

We are really blessed with a very mild climate pretty much all year round..being that we are surrounded by the sea and no part of Auckland being more than 15miles from the water...and at a lat of 37deg south we don't freeze our butts for terribly long..
It's 85 deg F. in my office at the moment, and the only bad thing about the city is the gridlock traffic in the weeks before xmas.

Can't wait to get away on the boat for a couple of weeks of windless nights & cold beers, then it's off to Sydney to sail my classic 18' in a wooden boat regatta for 10days..
Lifes tough down under..

Cheers PV

[frank sucevic]

[jon willy]

Very interesting subject ... has rings to it why they changed the polarity on motor vehicles.

MrW all the credentials for a trip to Tyneside.

Jon.
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why is the bit of wine I like always at the bottom of the bottle

[Paul V]

Hi folks..back to the origonal thread..yep it looks like the barge was the primary source of the stray current..poor/no maintainence/no anode protection/Simply a seagoing substation..The owners have now attached large zinc anodes to the hull of the barge and provided two large anodes that are hung from each side of my boat..
Will they come to the party and pick up the cost of the repairs?..well they have asked for me to forward estimates for the reasonable reinstatement of items affected by the electrolysis..
And what was the clincher? information forwarded by one of our own members from a US Web site..that stated "Galvanic corrosion may travel several hundred feet"..
Thanks to everyone who has offered advice and helped solve the mystery..and if you have got any rain to spare can you send us a bit..it's as dry as hell down under..

Cheers
PV.

[DAVE FROM NEWCASTLE]

great news paul glad you got that sorted and with out you haveing to spend a fortune fighting them
well done and enjoy your xmas and hope like me you have a sobber new year

a sobber geordie at new year never been heard off lol
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LOVE MY TROOPER 206,800 miles  AND STILL LIKE NEW EVEN THOUGH I DO TAKE IT OFF ROADING PLAYING AND EXTREME.
due to me driveing it to bulgaria and back and still running like new. now liveing in bulgaria

[Freskin]

Paul, First, isolate your boat from the shore power and any shore earth.
Don't confuse galvanic corrosion (caused by dissimilar metals in an electrolyte -seawater) with electrolitic corrosion which is caused by a current from an external source.(Can even be from your own batteries if you have poor wiring but suspect not in this instance)
The external source is using your boat as a ground path to the shore -most likely. As always it all depends!!
Severe damage can be done in a matter of hours in extreme cases.
It would be prudent to remove yourself as far as possible from the source. You are probably right about the barge but may need a surveyor with good knowledge of corrosion problems to prove your case.

Good luck
A marine surveyor

[Freskin]

Paul, only noticed the date on the postings so am sure you have the problem sorted out.
As a precautionary note. Don't assume the anodes will take care of the problem as they're main purpose is to handle galvanic corrosion, the zinc being the least noble of the surrounding submerged metals which of course would all have to be bonded or isolated.
-It all depends!!!

[Paul V]

Freskin..thanks for your comments..as you can imagine these guys called in their own band of so called experts and claim everything is normal with their barge..I suspect the test were undertaken without the barge being attached to shore power as it was working at the time and the pumps required to keep it afloat are then driven off the 24v system of the excavator situated on deck..

The facts are the barge had no annode protection at all for almost 7months and for almost 12hours of everyday is plugged into shore power.

My boat is moored approx 100 m away from the barge and is obviously not connected to shore power..so can I still be affected? I always isolate my batteries when leaving the boat and when I tested for stray current with my digital meter (neg to neg side of battery/ pos to external thru hull fitting)..nothing..

Is it possible that this barge can affect me or am I SIMPLY OUT OF MY DEPTH..

cHEERS pv

[Freskin]

Paul, it would be wrong of me to delve too much into this from a distance, this is a complex subject.
There are several possibilities, but your problem is not uncommon.
When I find such a problem, I often pass it on to a specialist in that field.
Yes the current can travel a long way, though I can't be specific - depends on the leak, it will take the path of least resistance.
Isolate everything on your boat and disconnect the negative battery terminal also.
What are your hanging zincs attached to. Should normally be the engine block earthing point.
Get someone to check the water surrounding the boat with a multimeter.
If you are getting over 0.8V, then you have stray current in the water.

AC and DC grounds must be isolated from each other -otherwise could be dangerous if there is a fault in the AC system - and cause the leak into the water.
The barge may use a transformer. It should be of the isolation type to prevent leakage to the DC ground. On board generators are also a potential source.

There are many books written on the subject and I warn you that you may not necessarily understand it all after the first read!!!
Have a word with a local qualified surveyor who. if not his particular strength should point you to a specialist in the field.
Get your likely cost agreed beforehand.
Should be similar or possibly less that a standard boat survey, alternatively could be charged by the hour.
You should get costs it back from the barge owners - if you prove your case!!!
In America there has recently been a tragic case of a child swimming around their boat when a current leakage from a marina shore source caused a heart attack and death of the child. It only takes a very small voltage.
It really scares me when I see so many boat owners with no more than an extension lead plugged ashore and plugged aboard into a ring circuit without any RCD or breakers.
A 120V system would be a safer shore system in marinas, same as we are required in workshops. The problem there is the requirement for heavier cabling - I digress.!!!
Regards
F

[Freskin]

I forgot - connect the + lead of the voltmeter to the boat's ground or engine negitive terminal and voltmeter - to a zinc 'guppy or large zinc mass and lower zinc into water. If your boat is protected through it's zincs, reading should be less than 0.2 V. Readings of 0.5 to 0.8 indicate a lack of zinc. Over 0.8 as said in previous post.
F

[Dafydd Wynn Williams]

May I congratulate Freskin on his post. I admire, and envy, chaps who can express themselves succinctly, and give clear, well-informed, useful advice.

Whist the subject is not immediately applicable, I have a general (but very sketchy) interest.

Thanks Freskin.

Dafydd W.W.

[mrwookie]

seconded

[Paul V]

... thanks for the info in laymans terms .. looks like i've got some more work to do when I get back from this Classic wooden boat regatta in Aussie..son of a preacherman are changing the rules to suit themselves before we even arrive..but as they say in all things Trans-Tasman.."Aussie rules mate"
I'm out of here on Wed for 11 days of sports drinking so look after the camp..
Cheers PV