Maxprop anodes

[rob2]

I wouldn't pay that for a haul out and anyway, how long do you need? A dry suit would be a good idea, but if you dry out against scrubbing piles you should get plenty of time to get the job done. If you pop down to the Hamble, there are two sets of public (harbour authority) piles or you could ask the various clubs if you could rent some time on theirs. Just be sure you have every conceivable tool and part you might need before the water starts to drop away!

Where are you based?

Rob.

 

[john_morris_uk]

I wouldn't pay that for a haul out and anyway, how long do you need? A dry suit would be a good idea, but if you dry out against scrubbing piles you should get plenty of time to get the job done. If you pop down to the Hamble, there are two sets of public (harbour authority) piles or you could ask the various clubs if you could rent some time on theirs. Just be sure you have every conceivable tool and part you might need before the water starts to drop away!

Where are you based?

Rob.

I agree - I didn't pay for haul outs last year as I dried the boat out against the wall at our sailing club. Easily enough time to scrub the bottom and sort out the anodes between tides.

 

[vyv_cox]

Yes I think that could be the reason. There is probably sufficient difference in the electrode potential of NAB and 316 stainless steel to cause the problems.

Such a pity because a plain manganese bronze prop will last for donkey's years without any need for anodes.

Aluminium bronzes have pretty good mechanical properties but presumably not good enough to make the props without resorting to stainless steel bits and pieces.
MG Duffs electro-eliminator.

Nickel-aluminium bronzes are somewhat subject to galvanic reactions with stainless steel. There is good general information on the subject here However, in the case of a propeller on a shaft the anode (in this case the propeller) is considerably larger than the cathode (the shaft and pins) and I would expect its corrosion rate to be extremely low.

I suspect that other factors may be involved, e.g. the material is not what the manufacturers state, some components of the prop have different compositions from others, externally applied currents, etc.

For info, the screws supplied with anodes for the Autoprop are made of nylon. When I first bought my Autoprop the screws were stainless steel, resulting in accelerated corrosion of the zinc around the fixing holes, so that the anode fell off half way through the season. With nylon screws the anode lasts for two seasons, with no localised corrosion. I also use a shaft anode, which loses some metal through the season, and the prop is still completely uncorroded after nearly 10 years. My shaft anodes last at least two seasons, maybe three.

 

[Ex-SolentBoy]

I really like the idea of nylon screws, and interesting that Autoprop now supply them as standard. I will talk to the Maxprop guys, but in the meantime can I have some advice please.

Suggested supplier?
How strong are they? I can imagine tightening them and them breaking.

Thanks

 

[Ex-SolentBoy]

I wouldn't pay that for a haul out and anyway, how long do you need? A dry suit would be a good idea, but if you dry out against scrubbing piles you should get plenty of time to get the job done. If you pop down to the Hamble, there are two sets of public (harbour authority) piles or you could ask the various clubs if you could rent some time on theirs. Just be sure you have every conceivable tool and part you might need before the water starts to drop away!

Where are you based?

Rob.

Unfortunately that is the going rate for local haulouts. Think I might go buy a crane!

I am Solent based, and yes, perhaps scrubbing piles are the way to go. I haven't tried it before. 18 ton boat - always been a bit scared.

 

[Seanick]

Had my anode go in 5 months on my 22" 4 blade variprop. At £55 EACH I took the new anode to my freindly foundry along with a collection of old anodes which they cast into 20 new anodes.
The new ones are solid, not hollow, with a sprue at one end so I cant stick it in a lathe and face it off, with a little hollow for the nut.
The fastening holes are easy to drill.

The new an6de has already lasted 9 months, although to be fair I have squeezed in a shaft anode too.

20 Anodes should see me out!

Re changing the anode........The old prop was removed, the new one fitted, and the apperture altered and re-sheathed between the tides whilst the boat (18 ton) was alongside.

Could have done without the mud though!!

 

[vyv_cox]

I really like the idea of nylon screws, and interesting that Autoprop now supply them as standard. I will talk to the Maxprop guys, but in the meantime can I have some advice please.

Suggested supplier?
How strong are they? I can imagine tightening them and them breaking.

Thanks

Nothing special about them, they are M5 nylon (from memory) about 20 mm long. Many chandlers stock them. I've never managed to break one and have yet to lose an anode due to one snapping.

 

[impact30]

Anode type

Thanks. Looked at the site. Which anode do you mean specifically. They say that they do not have the round Maxprop ones.

OOPs Solent boy, I should have done more homework!
Mine is the older triangular type...After extra shipping zincsmart are about 1/2 price of local swindlery!!!

On my first year I was caught unawares and by the time I checked the anode had disappeared completely...there was some rose coloured bronse evident when I cleaned the prop at end of season, so now I,m more careful!

On a related note, does anyone think the grease may make a difference?

Regards
Padraic

 

[PhilipH]

Adaptor

not sure it's 90% left, this is brand new I just bought from the MP dealer, it is rather hollow inside, the overall thickness seems to be around 10-15mm

same dilemma every year... :sad:

Hey Roberto - Happy New Year to you all. Just back in UK for quick visit - very cold. It's 35C in Salvador and 35F in NI.

At Southampton Boat Show I talked to darglow engineering and they have designed an adaptor plate that bolts to the end of the propeller using the three bolt holes and you can then attach the anode to the centre of the plate using a single bolt so that you get more wear out of the anodes. They plate was quite expensive, but given that my most recent anode lasted only 4 months, I may buy one. I change the anodes underwater (drysuit or wetsuit) and take some Sikaflex down on a wooden spatula and smear it over the bolt heads and along the line of the bolts - seems to help a bit.

Let us know how you are doing - Norma says hello too.
Best
Philip

 

[Ex-SolentBoy]

An update on this. I now have an adaptor plate from Darglow which allows the anode to be held on by a single screw in the centre. You can get this from www.darglow.co.uk

Of course, if you want to be really careful you can use a nylon one in the centre!

 

[TradewindSailor]

I hope you're not bolting the zincs on with nylon bolts. The stainless steel bolts are the best electrical connection you're going to get between the zinc and the propeller /shaft.

The problem is that when the zinc oxidizes in sea water ..... at the propeller/zinc interface .... the electrical contact becomes very weak. In order to protect the propeller and shaft the zinc needs to be at the same potential.

If your zinc is not being degraded ..... you propeller probably is!

 

[Monique]

I checked the price for a replacement Maxprop for my boat...

Anodes are cheap insurance even if they are not the perfect design. My opinion of course.

 

[njthake]

Why so much corrosion?

I have very recently been to Darglow Marine to discus the Maxprop with a view to replacing my fixed prop. I had heard of the anode problem from this forum and they explained the new bracket which allows you to fix an anode without the bolts and stop the local accelerated erosion of the anode in the area of the attachment bolts.
I have read various scary reports of heavy corrosion of the Maxprop and it’s protection and would like to understand more before shelling out a big price.
.
Are the similar components made from the same smelt?
How many different materials?
Is the lubricant/grease conductive?

I get alarm bells when I think of a mixture of metals, in a saline solution, periodically agitated, with the possibility of a positive electrical curent trying to escape.

I am sure that some people have no problems, I would really like to hear their story and try to work out why.

 

[vyv_cox]

I hope you're not bolting the zincs on with nylon bolts. The stainless steel bolts are the best electrical connection you're going to get between the zinc and the propeller /shaft.

The problem is that when the zinc oxidizes in sea water ..... at the propeller/zinc interface .... the electrical contact becomes very weak. In order to protect the propeller and shaft the zinc needs to be at the same potential.

If your zinc is not being degraded ..... you propeller probably is!

The bolts supplied by Brunton's for the Autoprop are nylon. Previously they were stainless steel but the anode corroded rapidly around the bolt holes and the anode fell off after a couple of months. Since using the nylon ones my anode lasts a season and is very obviously working.

 

[BabaYaga]

Isolate?

Hi all,

I’ve been reading this thread with much interest and would like to throw in a related (I think…) question.

Background: Since four years back I have a feathering prop on Baba Yaga produced by Australian company Hydralign (not represented i Europe). It’s made of ”high quality AB2 aluminium manganese bronze” and I don’t know if this makes it more or less vulnerable to galvanic corrosion compared to the Maxprop.
The zincs for my prop seems to be of the same type. That is dome shaped, in order to swallow the prop nut, and fastened to the prop hub by three stainless steel M6 (or M5) bolts.
I’ve experienced the same problem as the OP and others. The anode corrodes mostly around the bolt holes and has to be replaced although much of the zinc is still left. They are also equally expensive.
However, unlike some of the posters, I tend to get two seasons out of an anode before replacement is due.
In the much debated issue of bonding/interconnecting or not, I have chosen to refrain. That means that the prop and shaft on my boat are isolated from the engine and the electrical system (by means of a flexible coupling).
Does the panel think that isolating the prop/shaft might reduce the rate of corrosion/anode wear? Or instead increase the risk?
There are no signs of corrosion on the prop itself (or shaft) after four years. But maybe I have just been lycky?

 

[vyv_cox]

Hi all,

I’ve been reading this thread with much interest and would like to throw in a related (I think…) question.

Background: Since four years back I have a feathering prop on Baba Yaga produced by Australian company Hydralign (not represented i Europe). It’s made of ”high quality AB2 aluminium manganese bronze” and I don’t know if this makes it more or less vulnerable to galvanic corrosion compared to the Maxprop.
The zincs for my prop seems to be of the same type. That is dome shaped, in order to swallow the prop nut, and fastened to the prop hub by three stainless steel M6 (or M5) bolts.
I’ve experienced the same problem as the OP and others. The anode corrodes mostly around the bolt holes and has to be replaced although much of the zinc is still left. They are also equally expensive.
However, unlike some of the posters, I tend to get two seasons out of an anode before replacement is due.
In the much debated issue of bonding/interconnecting or not, I have chosen to refrain. That means that the prop and shaft on my boat are isolated from the engine and the electrical system (by means of a flexible coupling).
Does the panel think that isolating the prop/shaft might reduce the rate of corrosion/anode wear? Or instead increase the risk?
There are no signs of corrosion on the prop itself (or shaft) after four years. But maybe I have just been lycky?

AB2 is nickel-aluminium bronze, perhaps the best propeller material there is. It is very resistant to corrosion itself but like any other combination it may suffer from galvanic corrosion when coupled with something else. Assuming you have a stainless steel shaft I suspect this to be the driving force for your anode loss. I would fit a shaft anode if you can, this will reduce your anode loss and is the approach I have taken. I would certainly leave things as they are otherwise.

 

[Tranona]

Hi all,

Does the panel think that isolating the prop/shaft might reduce the rate of corrosion/anode wear? Or instead increase the risk?
There are no signs of corrosion on the prop itself (or shaft) after four years. But maybe I have just been lycky?

The only reason for bridging the flexible coupling is if you are bonding a hull mounted anode to the stern gear. The most common way is to bond to the engine because you can get a good connection, but obviously you need to make sure the shaft is still connected electrically to the engine. This is usually a bonding wire, but it is not always reliable and with some couplings like my Bullflex not even possible. An alternative is to use a brush type contact on the rotating shaft.

However, on many boats this is not necessary - if you have exposed shaft such as with a P bracket you can use a shaft anode. If there is space you can use a dome anode on the end of the prop, or if you have a folding or feathering propeller, rely on the prop anode. The disadvantage of this is that they tend to be small (compared with a hull anode) and therefore may not last as long.

On my boat, I originally bonded a hull anode to the engine with a bridge on the coupling, and also to the bronze stern tube because there was no room to get an anode on the prop or shaft. Now I have changed to a Bullflex coupling and a feathering propeller with a large anode on the end. Still bonded the hull anode to the stern tube. Both anodes erode, but at a slow rate and the hull anode slower than when it was connected to shaft and prop through the engine.

 

[Sailfree]

Opposite Problem!

I have a 4 bladed Variprop for 75HP engine. The boat (charter) is in a marina 11months a years , connected to the mains and the Prop Anode at each lift out is hardly erroded.

I did have an extra tear drop hull anode fitted in sight line to the prop and have the standard shaft anode and both these are severely erroded each year.

Last year I took a chance and did not replace the prop anode and when checked in August it was still OK.

Obviously as soon as I noticed that it weas not erroding much I checked continuity between it and the prop and then the shaft and finally all the other anodes and all made the meter buzz indicating a good circuit.

Any opinions?

Final question if shaft anode is half erroded do you fit an extra new shaft anode adjacent to it and leave the old one to further errode away or always replace it?