volvo sx...fizzing away...help!

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seventeen2

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Hello there!
Could anyone offer some information as to the right protection i need to stop galvanic corrosion eating away at my outdrives?
They are Volvo Penta SX and are only 2 years old, but recently having the boat lifted out, i was shocked to see blistering paint all over the gear casings.
The boat was moved from Wateringbury in Kent, to Hoo marina in Kent , and has only suffered since the introduction to salt water?
The anodes on the drives are factory fit aluminium, of which im told should be fine in all waters, although some say zinc is the awnser?
I really hope someone could help me out on this issue as im new to the boating scene and still finding my feet, but am worried about putting the drives back in un protected?
Thanks
 
Change your anodes regularly, don't wait for them to erode below 50%
make sure they are sea water anodes
Fit a galvanic isolator
Are you berthed near any old rusty metal (pontoon piling etc), if so berth your boat so that your outdrives are furthest away from the metal
Get an electrician to check your electrics and measure any current that may be causing damage - the galvanic isolator should neutralise this - they can be bought and fitted for less than £200
 
Do you have a galvanic isolator fitted if you are on shorepower? They are cheap and easy to fit and will almost certainly stop the problem. I had the same a few years ago and an isolator fixed it completely.

cheers,

Matt (no longer of Mananan, soon of Ummagumma)
 
Thanks for the replies fellas!
I dont leave the boat connected to shorepower, only when im there.
Would the aluminium type anodes be ok to use, or do you think zinc would be better?
I will definately look into an isolater unit, as im quite worried about the state of the drives? /forums/images/graemlins/frown.gif
 
As you probably know, zinc anodes are not suitable for fresh water but should be alright now that you are in salt water. However, I have heard that when zinc anodes are used in fresh water they can get a coating that stops them working in salt water afterwards.

I recommend that you replace your anodes with fresh ones and see if the problem continues.
 
I've got the same problem on my SX drives. The plate on the top of one of them has completely lost all the stove-enamelling. The other is fine so I guess it might be a manufacturing problem.

Also what anodes should I use in Teddington, Zinc or aluminium? The boat is moored on the Thames but will have 3 or 4 trips out to sea each year.
 
I'm Thames based with the occasional sea trip, I use Ali but have used Mag as well which would be ok if only in salt for a week or so. Zinc just limes up in freshwater which Teddington will be and is totaly ineffective.
 
I moor in fresh water in Weybridge but also take the boat down to estuary a few times each year. The boat has Volvo Penta 270 outdrives.

I use magnesium anodes and so far I have not noticed any significant corrosion although the anodes need to be replaced most years.

So far we have not stayed in salt water for more than about a week at a time and about two weeks total during the season. If I were to stay in salt water for a couple of weeks at atime then I think that I would switch to zinc anodes for the duration of the trip.

Hope this helps.
 
Either zinc or aluminium anodes can be used in salt water (Al for brackish and Mg for fresh)

If your boat has been in fresh water for any length of time with Zn or Al anodes they have probably become coated with a crust of oxide or carbonate which renders them ineffective even when the boat is taken into salt water.

You should therefore clean all oxide etc from the anodes!

MG Duff website is a useful source of info.

Aluminium anodes are cheaper than zincs and are said to last about 1¼ times as long.
 
Another alternative would be to fit the Volvo Penta Active Corrosion Protection System. This can respond to the level of galvanic activity in the water and produce an appropriate neutralising current. It draws about 3mA in the monitoring mode; more if it is required to produce current.

TJ
 
thank you very much for all the advice given, it is very much appreciated! It does seem to be a manufacturing problem on the sx drive as one disgruntled customer has actually posted the corrosion problem on u tube!
I will definately be renewing the anodes for fresh aluminium and fitting a galvanic isolator.....its going to be a lot cheaper than replacing the drives!
I need to obviously clean up the loose paint and respray, any advice given will also be greatly appreciated.
Also.....while im on, what are the galvanic isolators like to fit, is ok for the diy?
once again thanks
 
How about hang some extra anodes over the side. I have these 'danglies' connected to transom shield, and they are down 'in line of sight' of the props. Surely zinc is best in salt, aly is for brackish ? ... I'm not sure ..
 
[ QUOTE ]
Surely zinc is best in salt, aly is for brackish ? ... I'm not sure ..


[/ QUOTE ] As said earlier Zn OR Al for salt water, Al for brackish and Mg for freshwater.

Both Zn and Al become coated with oxide in fresh water rendering them ineffective, even if subsequently returned to salt water. Al, but not Zn, is satisfactory in brackish water. Mg is required in fresh water but is far too reactive to be used in salt or even brackish water.

Read what MG Duff have to say. Lots of useful info on their website with advice on the choice of anodes and on fitting them to hulls of different materials. http://www.mgduff.co.uk/

I am sure!
 
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