Volvo propeller corrosion

[roycharles]

I have fitted a new Volvo engine and saildrive at the beginning of the season with a Volvo two bladed folding prop.
The hub anodes are only lasting 6 weeks and there are signs of degrading on the propeller.
The saildrive anode Ok.
The boat is on a swinging mooring and electrically isolated when not in use.
The best advice from Volvo themselves is to take the prop back to the supplier, get a refund and buy a different prop! Very helpful I must say.
Any ideas?

 

[savageseadog]

We had the same problem with a Yanmar Saildrive combo, Kiwiprop was the solution.
Only other suggestion is to fit an anode to your keel and make sure the engine is earthed to it.

 

[crisjones]

We have D2-55 Volvos with saildrives and volvo 3 blade folders. My experience is the same as yours!!

Our three part hub anodes last approx 3 months and I know I really must check them asap because it is now just over 3 months since last change. The anode on the saildrive leg, that is only about 6" away is hardly wasted at all.

We are marina based, but I have fitted an isolation transformer and never leave the mains connected when we are not aboard.

Advice from Volvo was about as helpful as you got when I asked them how long the anodes should last. They said it depends on location and other factors etc etc!!! Would not give a sensible answer.

Local Volvo Service engineer has also commented that the anodes need checking very regularly so he is obviously aware that they disappear very quickly.

I have checked all the usual things - on ours the saildrive is actually insulated from the engine and hence the boats ac & dc electrics. My checks show that the insulation method works OK since I get very high (15 - 18 mega ohm) resistance readings between engine and saildrive.

Identical sister ship, 6 months old, in opposite berth also has the same high wear rate on anodes.

If any body has any solutions I would also be very interested.

 

[gettingready]

I have just had my boat hauled out for the winter and I have no anode left on the new prop (4 bladed folder) fitted in the Spring last year. The anode is a a ring around the hub and is custom to the propellor. There is not enough space on the shaft for a shaft anode. The propellor has some pink spots near the tips indicating that the prop has dezincified at least partially. Only having discovered this yesterday I have not contacted Volvo Penta but it sounds like I won't get much help. The prop was a big investment and it seems that I will have to do something more than just replacing the custom anode. Next year I intend to stay afloat for the winter so this will be more of a problem.

I have some good contacts at VP so I'll try and get some inside information on how bad this problem is.

 

[vyv_cox]

It appears that the alloy used for construction of these propellers is very active. Modern propellers are made from brass with small additions of other elements including tin, iron, manganese and aluminium. If these are added to the specification minimum or below then a material already not the greatest performer in seawater will be rendered even worse.

Your only answer seems to be to fit additional anodes, preferably on the shaft. If this is not possible fit one on the hull as close to the propeller as possible and connected to it electrically by a brush system inside the boat.

My Autoprop is fitted with a small anode at its hub but I also have a shaft anode about 3 inches from it. The prop anode lasts a season quite easily whereas the shaft anode lasts for two. Without the shaft anode the prop anode only made half a season.

 

[bigwow]

I have been using Volvo folding props, on my catamaran, for the last 13 yrs. The first ones I had the blades were held on by 2 little grub screws and the prop hubs had no anodes on them. I had no problems with corrosion just the occasional lost blade. The latest version, with the anode, seems to corrode within 12 months, in fact so badly that one of the teeth has broken off and the mating ends of the blades are bright pink. This leads me to think that the latest props are made of an inferior material and they try to compensate by fitting an extra anode. I did note that the latest leg anodes were Volvo price, Volvo packaged but when opened had “Made in China” stickers on them. I have reverted to the older type props, bought off Ebay, the only anodes now being on the legs.

 

[spannerman]

[I have checked all the usual things - on ours the saildrive is actually insulated from the engine and hence the boats ac & dc electrics. My checks show that the insulation method works OK since I get very high (15 - 18 mega ohm) resistance readings between engine and saildrive.

All Volvo saildrives and gearboxes on shaft drives on sail boats are (or should be) electrically isolated from each other, unless someone mistakenly attaches an earth wire to the gearbox or upper section of the saildrive, which will defeat the protection afforded by the anodes by completing the circuit between engine, keel, then via the sea to the prop and back to the engine, and shorten their life even more!

 

[Sailfree]

Had similar problems on a Volvo saildrive 2030 in 1998. Volvo replace under warantee twice before suggesting that they give me my money back and PLEASE buy any other prop you like.

Its a bad design in my opinion as dissimilar metals cause errossion at the SS screws and the annualar segments break at this point and get thrown off due to centrifugal force.

Bought another prop and no problems.

I have found the solution to Volvo problems [when the engine went on 2nd new boat)they did not want to know] is to only buy boats with no Volvo parts!!

 

[billmacfarlane]

This a well know problem on Maxi yachts as well. Volvo sent me a new prop, and all it done was to connect the prop to the leg anode which only lasted 3 months. I took the matter into my own hands and bought a Kiwi prop.

 

[roycharles]

Thanks guys,

Your comments have more or less confirmed what I suspected that the propeller is manufactured from an unsuitable material.
It seems that the electrolosis is taking place between the various metals that the prop is made from. How would a seperate anode help in this situation?
I think I may take up Volvo's offer of a refund and purchase a Kiwi prop

 

[roycharles]

Further thoughts.
If you bolt zinc anodes to a bronze propeller havn't you just created a perfect battery and therefore promoted electrical activity in the propeller? Could this be the cause of the propeller degradation?
I seem to remember from by school days physics that if you pass an electrical current between two dissimilar metals immersed in an electrolite (salt water) then one metal migrates to the other depending on the direction of the current.
The Volvo bronze folding prop I fitted to my previous saildrive unit did not have anodes and although there was increased errosion of the saildrive anode over the following two seasons, after that the anode errosion diminished back to a normal level.
Would the new propeller be better off without anodes?

So many questions. Does anyone have the answer? Volvo might but they aren't saying!

 

[crisjones]

Volvo have been manufacturing these propellors for quite a few years now, presumably from the same alloy mix all the time. They must be aware of the problem of anode wastage and electrolysis, and they must also know what causes it - ie is it the alloy used for the props.

Yet it seems that Volvo are not admitting to any knowledge of a problem and are just letting their customers deal with the problem. I have not heard of any other propellors needing to have anodes changed every 3 months. Seeing as Volvo are well aware of how and where their propellors will be used, I think it is appalling that we are expected to change anodes so frequently. Anodes should be expected to last 12 months in normal useage.

At the moment, the only solution I can think of is for Volvo to design and supply a larger anode that will, at least, last a reasonable length of time.

However past experience of Volvo's customer service does not indicate this is likely to happen!!!!

 

[vyv_cox]

"Volvo have been manufacturing these propellors for quite a few years now, presumably from the same alloy mix all the time. " Don't take that statement for granted.

Volvo are no different from any other company in seeing the benefits of moving manufacture to a country where the workers are paid £20 per week. Another way of reducing costs is to reduce the content of the more expensive alloying elements. In propeller bronzes there are very few of these to start off with, the alloy being basically brass with small additions of tin, iron, aluminium and manganese. However, every little helps and cutting out the tin altogether probably wouldn't make a massive difference to the performance, already not particularly good, but the effect on cost would be worth having.

Adding anodes is the only way to help to protect it. Banjo could do worse than reading the MGDuff website to clarify his knowledge. Electrons pass between the dissimilar metals, not the metals themselves. Electron transfer = corrosion, so making the anode corrode protects the propeller material. If the prop comes with its own anode, add a shaft anode and make sure the contacts between prop, shaft and anode are electrically good.

 

[Dennisail]

Hey guys. Very old thread but still the same issue. I have Yanmar SD20 sail drives and volvo 3 blade folders on my cat. I have had one hub replaced ($450) as I was scared the splines were no longer any good. My 3 piece anodes disappear at an alarming rate. Weeks, not months. The sail drive anodes last as long as you would expect, well over one year.

The issue is that if you are not replacing the volvo prop anodes every month the aluminium hub just corrodes away. What a stupid material to make hubs out of. Weak aluminium splines in an corroding Aluminium hub. Sure it looks bronze, but that is just the casing. The inside is Aluminium. So you have stainless steel spines from the sail drive, bronze hub casing then of course the Al hub is going to fizz away like crazy.

I am sitting here now at Pancake Creek with only one working prop thanks the splines finally giving way on the prop I did not have the Al hub replaced on. I am not going to keep replacing these alloy hub inserts for $450. Thats not the volvo price. Thats a prop specialist price. According to volvo you need to relplace they WHOLE hub and you cant even just replace the Al part. That costs like $900.

Anyway, this thread has confirmed my suspicion that its not just me that has this issue and that its a known defect from Volvo. So let the thread be bumped.

 

[Tranona]

Simple answer. Replace the props with FlexoFold.

This subject comes up here regularly and the problems are well known.

 

[Dennisail]

Every problem has an simple solution when you throw money at it. I had the chance to buy used flexo fold props for a good price when I first purchased the boat. Back then I did not know how shit these props were. What a mistake that was.

I mean they work great when it comes to propulsion. I tried to check the differences in speeds at various rev ranges etc compared to the fixed blade I put on there. The fixed blade prop had the advantage of pushing against a folded prop on the other hull when the folder had to push against a fixed prop and there was no real difference. I detected a slight performance advantage to the folder.

Many alloy outboard props simply have a plastic or rubber hub insert between the hub and a stainless spline. Even with power and torque greatly exceeding what my engines put out. I wonder if I can source some stainless splines from old outboard props of the same size then have a hard rubber bush machined up to suit...

 

[DJE]

My Autoprop is fitted with a small anode at its hub but I also have a shaft anode about 3 inches from it. The prop anode lasts a season quite easily whereas the shaft anode lasts for two. Without the shaft anode the prop anode only made half a season.

Thinking about fitting an Autoprop on my saildrive leg. Can't see how I would install an extra anode, so am I going to be replacing the prop anode twice per season or will the saildrive anode protect both the leg and the prop?

 

[vyv_cox]

Thinking about fitting an Autoprop on my saildrive leg. Can't see how I would install an extra anode, so am I going to be replacing the prop anode twice per season or will the saildrive anode protect both the leg and the prop?

Knowing the problems experienced by saildrives with anode problems I don't think I would rely on one to protect the prop. Painting the prop will help to preserve the anode - I have posted many times about the effectiveness of Velox. I would also talk to Bruntons. It may be that they have a solution.

 

[ex-Gladys]

Autoprops have an anode as the prop boss, at least conventional shaft ones do...

 

[rob2]

... will the saildrive anode protect both the leg and the prop?

The anode on the saildrive is to protect the leg only. The reason the prop is electrically isolated from the saildrive is that the leg would become the anode if the prop were in circuit. So the only anode that can protect a prop is the one attached directly to it. I wonder whether the manufacturers of stainless folders realise the potential market there is for saildrives?

Rob.