Missing Anodes!

[emandvee44]

Lifted out last week and this is what we found - propeller anode and one bolt missing after just 5 months in the water, mostly marina based. It would appear that the anode depleted around two of the bolts, came loose and with the prop. turning the third bolt came out.

The leg anode has also had a hard time probably as a result of the loss of the other one.

This is not a cry for help, just to bring to the attention of others who have saildrives and may find themselves unprotected after only a few months in the water.

If anyone knows a source of replacement anodes cheaper than the Volvo agents and Bruntons I would be very grateful.

Cheers,

Michael.

 

[vyv_cox]

The cause of the prop anode loss is that you are using stainless steel bolts. These promote a galvanic reaction that corrodes the zinc in the immediate area of the bolt heads and the anode is lost rapidly. Bruntons now provide nylon bolts as a replacement. I get two seasons out of my prop anode although I do use a shaft anode in conjunction.

 

[VicS]

The prop anode is going to waste pretty quickly come what may but the loss of the leg anode is a little worrying.. It should not be related to the loss of the prop anode.

I think I would want to investigate reasons for the rapid loss of the leg anode. Once that's gone the leg follows it fairly quickly!
If no reason can be found then a hanging anode as a back up might be a worthwhile investment.

 

[charles_reed]

The prop anode is going to waste pretty quickly come what may but the loss of the leg anode is a little worrying.. It should not be related to the loss of the prop anode.

I think I would want to investigate reasons for the rapid loss of the leg anode. Once that's gone the leg follows it fairly quickly!
If no reason can be found then a hanging anode as a back up might be a worthwhile investment.

In fact, because the prop is aluminium bronze it's very unlikely to waste, I get about 2 seasons out of my Brunton's nose anode.
As Vyv points out, the boss retaining bolts should be nylon - the SS are an unfortunate "improvement" by someone who doesn't know what they're about.
The nose anode usually drops off early, if you don't put a lick of paint round the bolt-holes - it corrodes there and the thing drops off.
A shaft anode is most desirable, otherwise you'll find the prop is quite OK but there's lots of pitting on the shaft.

Looking at the pic, I'd lay 10:1 the nose anode came off early in the season and the leg anode was left as the only sacrifice around. That shouldn't account for the excess wastage of that leg anode, as Vic points out, there is some other malign influence there which need investigation.

My Brunton has been in use for 18 years, just after they came out and it's one of the best improvements I made to the boat.

 

[Miker]

I paint the nylon bolts around the Brunton prop anode with antifouling. On lifting out of a marina after 7 months, the nose of the anode had gone and the shaft anode was worn away but will last another season. The prop anode was still firmly in place, though, as no wear had occurred around the antifouled bolt holes. On a previous season before antifouling the bolt holes, I, too, lost the prop anode.

 

[emandvee44]

anode loss

Just a quick note to thank you all for your very useful advice! I am sure as a result I can improve the anode life.

Michael.

 

[Ubergeekian]

The cause of the prop anode loss is that you are using stainless steel bolts. These promote a galvanic reaction that corrodes the zinc in the immediate area of the bolt heads and the anode is lost rapidly.

My shaft anode came with SS cap screws and nuts to hold the two halves together. Is that bad? I can't imaging nylon tightening up nearly enough for that ...

 

[davidej]

I'm with Miker on this.

We fit a genuine Brunton anode with plastic screws and its gone in half a season. Painting around the fixing holes with epoxy or a/f hasn't made any difference. Usually the screws are left with no trace of anode.

FWIW, we are on a swinging mooring in the Blackwater

 

[penfold]

Sounds like the prop anode needs to be redesigned with a steel armature cast into it for retention. I don't see the use of stainless fasteners as an issue; the prop is made mostly of bronze and the balance is SS anyway, and bronze is more noble than SS. If I had a brunton I'd be tempted to have a go at homebrewing something, as zinc is a straightforward metal to cast. What do Bruntons charge for a replacement?

OT how often do you have to change the bearings on an Autoprop?

 

[VicS]

and bronze is more noble than SS.

??

 

[penfold]

I stand corrected! Bronze, brass or zinc plated steel fasteners then, I can't stomach nylon in this role.

 

[emandvee44]

Anodes cost

In October 2009 the cost, from a Volvo agent in Plymouth, was:-

Stripper anode £32.40 + vat

Bruntons Propeller anode £39.50 + vat

(Labour for installation not included)

Obviously more now, so I am looking for a cheaper supplier.

I had the propeller bearings changed in March 09, and so far they are still good, but we have only done about 100 hours.


Michael.

 

[Quandary]

My shaft anode came with SS cap screws and nuts to hold the two halves together. Is that bad? I can't imaging nylon tightening up nearly enough for that ...

I used to lose shaft anodes because the rapid corrosion around the ss bolts loosened the grip on the shaft then they just wore away rapidly as the shaft spun. The solution I was told, was to put a dab of sealant in the bolt recesses, bedding and coating the head and nut, that part of the anode then remained sound and the reduction occurred generally around the circumference. I then used to get two years out of each anode though I replaced annually with one new and one part worn anode always in place on the shaft.
I would have expected that putting metal based antifouling on would accelerate depletion.

Nowadays I am stuck with a saildrive with the already high leg anode cost almost doubled because I have a rope cutter and a Volvo three blade folder with those tiny little anodes which must cost more per oz. than silver and have to be replaced every 6 months or so. Since there are no other sources for either I use a hanging anode which does considerably prolong the life of the leg anode but not the prop.
Against that cost and trouble though I now have a quieter engine and a bone dry bilge.

 

[vyv_cox]

My shaft anode came with SS cap screws and nuts to hold the two halves together. Is that bad? I can't imaging nylon tightening up nearly enough for that ...

No, several shaft anodes I have owned came with stainless cap screws and, as you say, they need some force to keep them tight through a season. The zinc will protect it well.

My Autoprop came originally with stainless steel screws but after a couple of years they changed them to nylon. I lost the first one in about half a season. Even now with nylon they are largely wasted at the end of a season unless I fit a shaft anode as well, but they don't fall off.

My Autoprop was fitted middle 2001, it is the greased bearing type. I have never changed the bearings and there is no indication that they need it.

So far as the corrosion of the prop is concerned I don't know what alloy they are made from. It does appear to me that the hub is different from the blades. I am positive the shaft nut is different. So there could be a bit of a mixture there, which is why the anode is important.

 

[davidej]

In October 2009 the cost, from a Volvo agent in Plymouth, was:-

Stripper anode £32.40 + vat

Bruntons Propeller anode £39.50 + vat

(Labour for installation not included)

Obviously more now, so I am looking for a cheaper supplier.

I had the propeller bearings changed in March 09, and so far they are still good, but we have only done about 100 hours.


Michael.

Does anyone know of a cheaper anode which will fit a brunton autoprop.

i ahve tried several of the usual sources withyout success

 

[rivonia]

In Mar-Menor last year we were lifted out at " Marina 2001"and had a lot of work done on the engines. We also had all anodes replaced. Later on many many miles away in Sicily we had to be lifted out again as one anode on the saildrive (we have two engines-a cat) had lost a bolt. The engineer whoo replaced the annode stated "the wrong bolts had been used"

Peter

 

[theforeman]

My shaft anode came with SS cap screws and nuts to hold the two halves together. Is that bad? I can't imaging nylon tightening up nearly enough for that ...

presumably your shaft anode is being tightened onto a stainless steel shaft. the ss bolts won`t affect that set up.
re the op there would appear to be 3 different metals involved - ss, bronze and zinc. makes sense to remove one of them from the equation.

 

[emandvee44]

Missing anodes!

Re the foreman
I think there are more than three different metals involved.
Propeller, propeller blades, ss bolts (both securing the blades and the prop. anode) the rope cutter is ss, and possibly the propeller securing nut as suggested elsewhere in this thread. I do not count the anodes!

I am going to buy two of each, stripper anodes direct from Ambassador Marine (who have an online shop), and hopefully Volvo (or a Volvo agent). Must be cheaper than locally here.

Also, I did notice that my neighbours in the marina use clump anodes hung over the stern.

Now to find some cheaper anti-fouling....................

And equivalent spec. oil for the engine.

Cheers,

Michael.

 

[samwise]

Just finished our first season with a Darglow Featherstream prop and the nose anode looks to be in pretty good shape and should go another season. However, like the Bruntons, there is not that much anode "meat" around the securing bolts so I suspect the unit will suffer the same problem in due course. I always have two shaft anodes installed, replacing them alternately, plus a hull pear. Don't know the price of the Darglow anode, but I guess it's time to find out!