Volvo Penta Saildrive anodes

[wiggy]

My prop anode lasts well short of half a season (swinging mooring) before it vanishes, the leg anode lasts far better and I'll get 2 seasons before its anywhere near 50% worn. Is this normal?

 

[colhel]

I'm on a swinging mooring in Poole and have the same results as you. Have to say was quite alarmed at the state of the prop anodes, but like you the leg one seems okay.

 

[Tranona]

Some makes of prop are well known for high anode wastage. Nothing you can do about it unless you can get bigger anodes. Others don't even need anodes - not that its much help to you unless you buy a new prop.

2 seasons is OK for the main leg anode.

 

[Lucky Duck]

Unfortunatley I have this exact issue on my current boat and also 'enjoyed' this feature on my last boat which was also a Frist 31.7. As far as I can tell it appears to affect all boats with Volvo folding propellors on thier saildrives.

To improve the life of my folding prop I have learnt to put the boat on the piles sometime during the second hald of September time for a scrub and to change the anodes at the same time. Alternatively I know some boat owners who have changed to a kiwi prop to avoid this problem.

 

[Tranona]

A Flexofold (which I have on a saildrive) does not need anodes.

 

[nigelmercier]

My prop anode lasts well short of half a season...

You could try painting it

I get about 2 years out of mine, with a painted propeller and saildrive leg.

 

[VicS]

I am afraid it is inevitable that if you put a smallish chunk of zinc on a propeller, with a relatively large surface area, made of a copper alloy such as a brass, bronze or nickel aluminium bronze and immerse it an electrolyte such as sea water the zinc will corrode rapidly. ..... dissimilar metals, galvanic corrosion and all that stuff with ...... a potential difference of around 0.7 to 0.8 volt driving it.

Tranona says his Flexofold does not require an anode, it is presumably, therefore, a two bladed one because the three bladed ones do have anodes despite the major components of both being nickel aluminium bronze.
Presumably other materials used in the construction of the three balded ones make the anodes necessary.
Nickel aluminium bronze itself is one of the most corrosion resistant materials used in the manufacture of propellers

 

[AIDY]

You could try painting it

I get about 2 years out of mine, with a painted propeller and saildrive leg.

lucky U..... i paint mine prop anode lasts 6 months saildrive ring about 2 years.

 

[VicS]

lucky U..... i paint mine prop anode lasts 6 months saildrive ring about 2 years.

Painting the prop, if you can find a coating system that will adhere, might be a sensible way of extending the anode life but painting the anode rather defeats the object of fitting it!

 

[PeterR]

Everyone with Volvo saildrives and folding props seem to have the same problem with the 3 sections of the prop anode disappearing before the end of the season. With my present boat, after the second season of this happening I antifouled a small strip of each anode around the bolt attachments. This has ensured the middle of the anode where the metal is thinnest around the bolt hole is not eroded so the rest of the anode is not flung off by centrifugal forces and now at the end of each season they are still there, heavily eroded but functional.

Previously, antifouling the prop reduced anode wear but not enough to make them last a season. Fitting a galvanic isolator this season has also reduced the amount of anode loss.

 

[PabloPicasso]

I had terrible problems with prop annodes erroding in a couple of months. I stopped using copper based antifoul on the saildrive and this has helped enormously.

 

[Lucky Duck]

At the risk of stating the obvious :- copper based anti-fouling should never be used on the saildrive leg. Most manufacturers offer a copper free product specifically for use on saildrives such as International's Prop-O-Drev.

 

[nigelmercier]

At the risk of stating the obvious :- copper based anti-fouling should never be used on the saildrive leg...

Quite so. And I was joking about painting the anode