Electrolosis

[madman1]

My Stacer 525 Cuddy is now approaching 12 months old and small bubbles in the paint are forming around the ski hooks, guages and ariel socket.

I have talked to the dealer and he suggests it is my fault as the depth sounder, cigarette socket and CD player are earthted only to the side of the boat, not a central location towards the rear of the boat. They are suggesting the boat is now live.

I am the first to admit I know nothing about marine electronics but conversations with Rocketfishman (Nathan) suggest these guys are full of sh!t and dont want to deal with the wrath of Madman1 once again.

So I thought would put this thread forward as I dont think I am the only one out there with no marine electronics knowledge.

Hopefully someone has the answer before I go nuts at these guys once again.

Cheers


Mark

[Big_unit]

Sometimes talking to another dealer works cause often they are more than happy to point out the things that your dealer wont address. A calculated approach will get a result.

Cheers
James

[JB]

Your right mark , they are full of shit. But unfortunately im not sure if there is much you can do about it. I have the same problems with several fittings on my boat, and have seen the same problems on pretty much every tinnie. They fit stainless or metalic items to the alloy without using duralock (can buy this at whitworths etc) or a rubber to seperate the metals. Only thing u can do is pull out things like ski hooks and padd them with rubber or duralock between the metals to stop the corrosion.

Others may be able to give you more technical details on why and how to fix.

Jas

[Heath]

As far as the paint bubbling around fittings, it is a regular thing with painted tinnies. To happen in just under 12 months is a bit unusal I would think. It generally takes a few years to appear. But in saying that, having the sounder, socket & CD player earthed to the side of the boat is wrong! Remove that setup immediatly. Did you get them wired professionally? If you did, you should go back & give them a blast. No equipment should use the hull as an earth return. :-/

Did this have any bearing on your problem? I don't know, but it could have speed up the process.

[snapattack]

First thing. I don,t think any electrical device should be earthed anywhere on a tinny. Should only earth back to the battery.

Try putting a sacfrificial anode on the back of the boat below the waterline. That will slow the process.

Seperating metals, I think, is a waste of time unless you plan to use plastic screws or bolts to join them back together. The dissimilar metal reaction will continue even if you seperate the metals with something. The screw or bolt will still provide some contact to connect the two together.

I would redo the wiring so that nothing is earthed to the boat. Just run all the negative wires back to the battery.

Hopefully this helps.

[frankj]

I don't think you should earth your electrical system to the boat at all, ensure it is isolated. If you have more than one earth, whether intended or inadvertant, you will get minor circulating currents which will cause or increase the effects of electrolysis.
When the boat is not being used isolate the battery.

There have been a number of past posts on this subject, do a search and you'll find lots of information.

Regards
Frankj

[Fisher_Boats]

Mark,
The comments above are right. Don't earth anything.
You can run everything to buzz bars to save running a heap of wires.You can get insulated cigarette sockets.
Duralac and where possible plastic or rubber between fittings will help.

Cheers
Col

[Mr_Bean]

Agree with the post above, but do do something about the corrosion NOW.

Remove the ski hooks etc and sand the affected areas clean, then prime and touch up the top coat. If you do not do this it will continue rapidly beneath the paint and keep blistering ahead of you.

Main points have been covered but when reassembling you must use a jointing compound (Duralac) to exclude all moisture when in contact with salt. Like battery cell it will continue to react between the dissimilar metals.

Like any form of cancer, act now.

See here: http://www.whitworths.com.au/main_itemdetail.asp?item=59733&search123=duralac&intAbsolutePage=1

Mark, do the earth connections actually run through the hull? Or are they saying because they don't connect near the rear? Something smelly here me thinks!!!!!

- Darren

[john_laura]

Who did the wireing? :o

I agree with the other's, remove the earth wires from the hull and send them all to a buzz bar and the back to the battery. Fit a battery isolater also if possible.

Sounds like whoever did the fit out cut corners.
John

[Mr__Bean]

Madman,

Do not accept that this is a wiring issue.

Sure, stray current will cause electrolysis but this will occur at the surfaces in contact with the water. That is, the bottom of the boat will fizz and corrode when in the water.

What you describe here is "galvanic corrosion" between dissimilar metals, it is happening where stainless screws and/or fittings have been used without proper jointing compound.

A direct result of workmanship.

- Darren

[NQCairns]

I am with Mr Bean on this, sounds galvanic. How does one isolate an earthed motor from an ally hull totally anyway?? Electrolosis starts anywhere wetted on metal it is not choosy, galvanic must always start at the interface between differing metals. On a table I saw once I think aluminium and SS were a fair way apart so not a good choice to fit together so if they did nothing to excude an electrolite from contacting both and making a battery corrosion will happen, manufacturers/fitters really should be pulled up on this! imagine if the door handle on your new car caused rust bubbling paintwork around it after a year of normal sevice!!!! and this was considered acceptable. nq

[Mr__Bean]

While we are on the topic of jointing compounds and ways to protect your tinny, here are some shots of mine, hope it helps.

When placing any screws in they must be put in with Duralac or other recognised marine jointing compound. See the yellow Duralac around the side window frame mounting screws.

[Mr__Bean]

See also the Duralac in the pissy little screws that hold the switch in place, you must use it on all installations

[Mr__Bean]

For large areas like rod holders and antenna mounts first sit them on a bed of Sikaflex sealant, then install the screws with either Sikaflex or Duralac.

[Mr__Bean]

When you have a tow cover or bimini installed, make sure they use nylon washers under the Press Studs

[Mr__Bean]

Skin fittings must also be insulated, Sikaflex once again.

Note the nylon washer under the Press Stud again.

[Mr__Bean]

Hope these help people understand what is involved to properly prevent galvanic corrosion.

I agree strongly with the earlier post that dealers have got away with poor workmanship for far too long now.

Something to think about when screwing best price out of them though, make sure you stipulate that all fittings are to be installed with jointing compound.

- Darren

[dnej]

Stainless is a good as you can do, as aluminium screws etc are as scarce as hens teeth. Get some lanolin grease, not the spray on type, coat the thread and head of the screws with Lanolin.
Also use the grease under the fitting. Also a bed of Sikaflex, under the fitting helps, but the Lanolin and the Sika, dont like one another, so I have stuck with the Lanolin, grease. Give me an email , and I will organise the grease for you.
Regards David