What type of anodes?

Chill

Chill

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I need to replace the anodes and have always used Magnesium but a friend said he uses Aluminium which are also effective when used at sea.

Which ones are best? will be using the boat mainley on upper thames with a couple of trips per year into the sea.

Thanks

Geoff
 
Conventional wisdom is Magnesium for fresh water, Aluminium for brackish water ( Esturine ), and Zinc for salt.

If you are mainly on the Upper Thames you are correctly using Magnesium.
 
Thanks for that guys,
Now I need to find a pair of Magnesium Hull anodes 440mm long with 195mm hole centres. Most places only seem to list the smaller ones!
 
Go magnesium on upper thames - ali won't offer the same protection.[/QUOTE]

Out of interest.... how long should they last on the Upper Thames? I have yet to get the boat out for antifoul and anodes and was thinking about leaving it until Sept. Most of out boating has been on the Upper Thames (on Magnesium) with a month on the salty stuff last summer.
 
thejonesey said:
Go magnesium on upper thames - ali won't offer the same protection.
Click to expand...

Out of interest.... how long should they last on the Upper Thames? I have yet to get the boat out for antifoul and anodes and was thinking about leaving it until Sept. Most of out boating has been on the Upper Thames (on Magnesium) with a month on the salty stuff last summer.[/QUOTE]

That depends very much on where you keep it. In a busy marina with lots of hook ups I would want to at least check mine annually. I have recently had my boat out and the anodes have clearly been doing their job for the past 12 months and will certainly last till the winter lift out.
 
On my previous boat (40ft twin screw steel jobbie moored in Penton Hook) the anodes lasted five years and even then weren't in really bad shape. New boat will come out for this winter after a little over two years afloat so it will be interesting to see how they look.
 
27foot fibreglass boat - twin shafts - new magnesium anodes approx 2½ years ago. Boat has spent most of that time on the non tidal in both Bray and PH marinas but 5 weeks last summer on the Medway.
Lifted about a month ago and anodes roughly 50% depleted so definitely doing their job and replaced them.
 
Difficult to say Rob. Had my boat lifted a month ago for the first time in three years, and although significantly depleted, I probably could have left them on for another year, just.

I'm moored adjacent to earthed pilings, so expect some galvanic action.

Looking at wavey, b1 and my experience, I would say you're probably ok for three years up here.
 
Should the anodes be scrubbed/ cleaned in between lifting, do they lose their effectivness if covered in green slime/algie

I go under with my mask and snorkel every year in the summer to check me props and last year (been in 2 years) the anodes had plenty of meat left on them.

Have just fitted Mag anodes thanks for the input everyone. got them from anodeoutlet.co.uk great price and delivered 9am next day
 
Chill said:
Should the anodes be scrubbed/ cleaned in between lifting, do they lose their effectivness if covered in green slime/algie

I go under with my mask and snorkel every year in the summer to check me props and last year (been in 2 years) the anodes had plenty of meat left on them.

Have just fitted Mag anodes thanks for the input everyone. got them from anodeoutlet.co.uk great price and delivered 9am next day
Click to expand...

They do say don't anti foul them. Never heard of slime build up being a problem however.
 
I'm on outdrives so no hull anodes, when I first had the boat used Mag and they limed up, as I was reguarly doing a month or so at sea I switched to Ali on the outdrive ring and block anodes and they seem fine last about 3-4 years and don't fizz away in the sea like mag do.
 
Called for a price of mag anode kit for my bravo 3 drive today. They were telling me to use Ali anodes in the non-tidalThames although 2 years ago on a service they fitted mag anodes which are now due for replacement.
What I don't understand if used ali and the drive unit is made of ali then how does the ali anode work in protecting the leg casing?
 
russ said:
Called for a price of mag anode kit for my bravo 3 drive today. They were telling me to use Ali anodes in the non-tidalThames although 2 years ago on a service they fitted mag anodes which are now due for replacement.
What I don't understand if used ali and the drive unit is made of ali then how does the ali anode work in protecting the leg casing?
Click to expand...

The Ali ones are an alloy and not pure aluminium so they are less noble than the outdrives and react first, i've used them sucessfully for at least 5 years on the non tidal.
 
Chris_d said:
The Ali ones are an alloy and not pure aluminium so they are less noble than the outdrives and react first,
Click to expand...

I very much doubt the outdrives are pure aluminium, more likely a stronger aluminium/copper alloy, but yes the trick is to use a material for the anode that will erode at a faster rate than the items you are trying to protect. I must admit that I always thought that magnesium was the way to go in fresh water
 
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