What now skipper - anode trouble

[Hugo_Andreae]

We've got a slightly different conundrum for you this month about how to diagnose a case of fizzing anodes. Read the scenario below and let us know what steps you would take to diagnose and resolve the problem. The best and/or funniest answers will be printed in next month's MBY magazine. Thanks...Hugo

"A new, better paying job has allowed you to swap your 25ft trailer boat for a snazzy one-year-old 42ft sterndrive sportscruiser and a berth in a convenient full-service marina. Fuel and water on tap and permanent shore power – what bliss. But six weeks later during a routine check you notice that the paint on the sterndrives – which was previously perfect – is showing signs of blistering and the new anodes have almost disappeared. What now, skip?"

 

[KevB]

Firstly replace anodes making sure they are the correct type for the type of water. (maybe this will cure problem)

Fit a calvanic isolator as a matter of course.

Unplug all the boats around you as you leave the marina on sunday nights in case one of the gits around you has a earth leakage problem....

Sorted.

 

[awol]

Do nothing - come November it will only be of any use as a floating caravan and you won't be going anywhere anyway.

 

[Whitelighter]

right. You wish sunshine....

 

[fireball]

Phone up the dealer and get them to sort it ...
if they won't then call an engineer - with all that extra dosh it's only fair to spread it around .... /forums/images/graemlins/wink.gif

 

[mainshiptom]

Move your boat out of that marina.

Sit your boat on lovely mud in the east coast and make a hugh saving.

Tom

 

[longjohnsilver]

Bring it ashore asap and leave it sitting there, will save a fortune in anodes and marina fees whilst you search for a proper motor boat with shafts.

 

[D3B]

Find another marina after replacing the anodes and fitting a Galvanic isolator

Youre probably moored in Chatham Dock Yard.... /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif

Cant be anywhere else really after all the rubbish that was thrown overboard when the navy finished doing refits /forums/images/graemlins/shocked.gif /forums/images/graemlins/blush.gif

 

[Divemaster1]

 

[Bloater]

Has some sod craned it out and swapped your outdrive and anodes for some inferior ones when you were away?

 

[Divemaster1]

On a more serious note:

Did the boat previously run in fresh water, or has it been recently serviced ... if so, suspect anodes and take the appropriate action of checking with yard who fitted the anodes/broker who should have sold the boat as "fit for purpose" and arrange for a lift out accordingly for replacement anodes and assess drive damage (Cosmetic of structural). Severity determines action and remedy / negtiations with yard / broker.

If not the above, then there is a earth leakage somewhere ... Switch off fuse and unplug own lead to boat. Check other boats on pontoons (not just your own, as you may be the source) for similar damage. If consistent with yours, then go to marina office and have them investigate earth leakage on the feed to your pontoon and make sure that they contact owners of boats on same pontoon. If no earthe leakage is found with your boat un-plugged, you'll be the source, which needs to be checked and resolved.

If yours is the only one, you need to take appropriate action to resolve issue and book liftout for fix and new anodes.

 

[Remmington]

Smear on Preparation H

 

[Hurricane]

Fundimentally, I agree with Divemaster1.
There would appear to be earth leakage somewhere.

Having actually had similar problems I did quite a lot of research on this.

Firstly, I would check the natural Galvanic voltage. This is the natural voltage that is obtained when you connect zinc (the anodes) with a dissimilar metal like bronze or stainless steel. Metals are rated galvanically (so to speak) on a scale called the Noble Scale. If two metals have a large difference between their Noble values, they will generate a voltage when joined together and immersed in water. Stainless steel and bronze have similar values but when either of them are used with zinc about 1.4v will be generated. Where you have a voltage, a current will flow and this will eat away at (hopefully) the sacrificial anodes.

So, firstly disconnect the shore supply (completely).
Then connect a multimeter between an anode and a shaft or good earth on the engine. You should get about 1.4v if the anodes are working correctly.
Now reconnect the shore supply and if the voltage rises then there IS a leak.
It will then be a matter of isolating everything on the boat and gradually switching it all back on again until you find the circuit that is causing the problem.

If the voltage is increased when you simply connect your shore cable to the boat and everything else is disconnected, there may be a leak external to your boat. If another boat, for example, has a leak, it can be leaking electricity down the shore supply's earth. The shore supply is probably earthed at the shore. Again, where there is a current flowing, there will be a voltage. This can, of course, build up on the shore supply's earth wire and when it gets to your boat will cause a secondary flow of current into your nicely protected galvanic system. The solution here is to fit either a transformer (to completely isolate your boat from the shore supply) or, as is more often used, fit a Galvanic Isolator where the shore supply's earth connects to your boat. A Galvanic Isolator is simply two huge diodes connected "back to back". These diodes (being silicon) have a resistance and will only pass current across a voltage greater than a few volts. So if you DO get a genuine electrical failure, the shore supply's earth can be used even if it is at a higher voltage caused by another craft.

Most boats with shore electrics will have galvanic isolatore fitted by the manufacturers so it may be a matter of checking if these are working. To do this, disconnect everything and use a diode tester - each way of course.

This is what I found when I did my research. My problem was that the shatf brushes were badly worn and it was a very simple fix. I'm no expert but when I get problems like this, I use the internet to research into the problem.

 

[KevB]

[ QUOTE ]
Fundimentally, I agree with Divemaster1.


[/ QUOTE ]

Which is exactly what I said only he used a few more words... /forums/images/graemlins/grin.gif

 

[Divemaster1]

[ QUOTE ]
[ QUOTE ]
Fundimentally, I agree with Divemaster1.


[/ QUOTE ]

Which is exactly what I said only he used a few more words... /forums/images/graemlins/grin.gif

[/ QUOTE ]

Well Hurricane used even more .... so we all agree then ... off for a pint to celebrate then??? /forums/images/graemlins/smirk.gif

 

[KevB]

/forums/images/graemlins/smirk.gif

 

[ostria]

Sequential actions:

1. Unplug from shore power
2. Change anodes
3. Fit galvanic isolator if not already done
4. Grab wiring diagrams (one year old boat means they exist /forums/images/graemlins/smile.gif ) and use the multimeter as much as possible /forums/images/graemlins/shocked.gif

 

[wongaero]

Get the the marina to stop using my boat as an earth connection! I'd guess the shore supply needs earthing properly - maybe they coincidentally have a large supply of galvanic isolators for sale in their swindlery...

 

[sunquest]

[ QUOTE ]

Youre probably moored in Chatham Dock Yard.... /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif

Cant be anywhere else really after all the rubbish that was thrown overboard when the navy finished doing refits /forums/images/graemlins/shocked.gif /forums/images/graemlins/blush.gif

[/ QUOTE ]

Oi behave! /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif

 

[alan006]

Here's a suggested plan of action.
a) Find out if it is a problem caused by the shore supply. I am assuming that the boat does not have an isolating transformer. If it does then this testing is not needed.
1) Get an old anode and attach a conducting wire to it and lower it into the water near your boat. Now, using a multimeter measure the voltage between this and the earth on the shore supply. A typical reading will be less than 0.25 volts ac. This is acceptable. If you find any dc voltage then this is not acceptable and needs to be investigated. Leaving the meter connected simply pull out the plugs of the boats near yours watching the meter for any changes. The moment you see a change on the meter you are identifying the source of the problem. Note, a galvonic isolator will only protect you from very small voltage problems. If the voltage comming down the earth wire is more than about 0.7 volts it won't protect your boat. The only way to be certain is to have an isolating transformer. ( I suggest this testing is done by the marina, they might not be happy at people doing this themselves).
b) If the problem is not caused by the mains shore supply, then there are several things to check.
1) Has any metallic debris been left on the marina seabed underneath your boat. This can cause severe problems.
2) Has any neighbouring boat failed to keep renewing its anodes and if not they might be "sharing" your anodes.
3) Are surrounding boats having a simular problem or is it only you.
c) Having asked these questions and hopefully shed some light on it, get the boat lifted to have a proper look. Renew anodes where necessary, repair protective paint to outdrives where needed, check with the multimeter for continuity with the anodes to all skinfittings and outdrives. Check bonding straps on the outdrives are in good condition.