Prop shaft anode

[AllanG]

After lifting my single engine boat a couple of weeks ago, I found the Volvo prop anode totally missing, which I believe isn't unusual.

When refitting a new one, I've been advised to use a small amount of Sikaflex on the threads, leaving sufficient thread clean for good anode to shaft contact...........does anyone else use this method?

I'm also thinking of adding a MG Duff shaft collar anode to supplement the Volvo one, (there isn't enough space to fit the MG Duff shaft anode with the steel insert)......my only concerns are how to ensure the anode remains tight on the shaft, and if it will cause any unwanted prop shaft vibrations.

Alternatively, I'm considering the MG Duff Electro Eliminator kit to fit inboard on the prop shaft, and connect this to my hull anode.

Any advice on either alternative would be greatly appreciated?

Many thanks,

Allan

 

[Bandit]

I use both a shaft anode and an electro eliminator kit and I have the connectivity checked, props are expensive things ( having lost a pair to electrolosis in the past).

I have also seen shaft anodes drop back on the shaft to block the P bracket cutless bearing and also to ride up to damage the hull.

I now always fit a stainless jubilee clip above and below the anode to stop it moving with the clip tail trailing when the shaft is running ahead so it does not snag debris.

 

[DAKA]

If your boat has a modern quality metal used in the shaft and the prop then a zinc anode doesnt do anything other than make its own circuit to erode itself.

Shaft anodes are not required on modern quality boats.

they are a throw back to the old days of brass props and steel shafts.

Bronze and stainless (316) is still a bit of a problem with slightly dissimilar metals but a quality TeMet shaft and a quality prop both have the same electrical qualities and both are corrosion resistant.

 

[Latestarter1]

If your boat has a modern quality metal used in the shaft and the prop then a zinc anode doesnt do anything other than make its own circuit to erode itself.

Shaft anodes are not required on modern quality boats.

they are a throw back to the old days of brass props and steel shafts.

Bronze and stainless is still a bit of a problem with slightly dissimilar metals but a quality T-Met shaft and a quality prop both have the same electrical qualities and both are corrosion resistant.

Hear hear!

Shaft anodes.........smply nuts.

 

[Ripster]

If you do a search on shaft anodes and how to fit them - on here - you'll see plenty of advice. The key to shaft anodes, which work fine and do not move if they are good quality with an inner ring and are fitted properly, is to hit both sides with two hammers simultaneously to seat the anodes properly to the curve of the shaft.

So tighten the bolts up reasonably then make the joint hit on the solid sides 90 degs to the joins - this seats them down on the shaft and you'll get some more turning on the bolts - I do this about 3 times, until the bolts do not loosen. Put a bit of thread lock on the bolts too and use nyloc nuts. As a word of caution - assume you would have already sussed this - but dont hit them on one side only or you may damage the shaft or associated kit. Some say you can brace one side with a large hammer, then hit the other, but dual sim strikes are the safest IMO.

As said, if done properly, decent anodes will not move on the shaft - no need for clips or glue. I got mine from here www.zincsmart.com

 

[Trundlebug]

All the shaft anodes I've fitted seemed to have locking threads on them. Once fitted they couldn't be easily undone without stripping the threads.

Having read of them undoing themselves / coming loose / falling off / sliding up and down I've been conscious of doing them tight, but they're so difficult to turn in either direction I can't ever see it being a problem.

Interesting to read they may not be necessary after all; can't help but feel belt and braces isn't a bad thing with expensive items though

 

[PaulGooch]

1) If the shaft is attached to the transmission via a flexible coupling that electrically isolates it from the transmission and is supported by a cutlass bearing, it is just a lump of metal in the water. Why does it need an anode ?

2) If it is attached to the transmission by a solid coupling it is electrically connected to the engine. If the engine/transmission is connected to the anode bonding circuit, why does the shaft need an anode ?

 

[Tranona]

1) If the shaft is attached to the transmission via a flexible coupling that electrically isolates it from the transmission and is supported by a cutlass bearing, it is just a lump of metal in the water. Why does it need an anode ?

2) If it is attached to the transmission by a solid coupling it is electrically connected to the engine. If the engine/transmission is connected to the anode bonding circuit, why does the shaft need an anode ?

The anode is to protect the prop, not the shaft. It is therefore electrically bonded to both and in view of the prop. If you have secure bonding to a hull anode it is not really necessary, but in reality getting a good bond is not always easy. So a shaft anode can be useful, but of course not ideal as it interferes with waterflow and can come loose, so some folks don't like them. Anodes on the end of the prop are an alternative, but usually are relatively small. The problem the OP has is that there is not enough exposed shaft to fit one of the larger, more secure shaft anodes, so his alternative to increase his anode "capacity" is a hull anode, probably with an eliminator for connection to the shaft - if he has room behind the coupling inside the boat.

 

[n.herring]

1) If the shaft is attached to the transmission via a flexible coupling that electrically isolates it from the transmission and is supported by a cutlass bearing, it is just a lump of metal in the water. Why does it need an anode ?

2) If it is attached to the transmission by a solid coupling it is electrically connected to the engine. If the engine/transmission is connected to the anode bonding circuit, why does the shaft need an anode ?

The shaft needs an anode so that I do not get another bill for £2000 for 2 more props, as happened about 4 years ago on previous boat.
When lifted last spring single shaft anode had vitually gone after 8 months in the hamble water. This time have 2 shaft anodes on each side, as someone else said where this is concerned belt and braces every time.

 

[Latestarter1]

The shaft needs an anode so that I do not get another bill for £2000 for 2 more props, as happened about 4 years ago on previous boat.
When lifted last spring single shaft anode had vitually gone after 8 months in the hamble water. This time have 2 shaft anodes on each side, as someone else said where this is concerned belt and braces every time.

If your props were subject to dezincification then they were poor quality, nothing to do with Hamble water vessel has rampant electrolitic issues.

Class 1 Nibrals will highly resistant to dezincification and other forms of corrosion.

Shaft anodes have their place with old fashoned bronze stern gear and slow shaft speeds.

Moden vessels have high shaft speeds and SHOULD have Nibral props. I pay a lot of attention to shaft diameter and strut design including machining a nice nylon fairing piece by leaving the cutless bearing proud of he strut. Having some goon putting a potential hand grenade on the shaft creating a complete mess of the laminar flow to the prop is simply brainless.

In addition to screwing up laminar flow as soon as anode suffers material loss you have out of balance force on the shafting leading to rumbling and potential hull damage.

 

[PhilipF]

I notice Alan said "prop" anode, but the majority of responses respond as if "shaft" anode.

We have the same make of boat as Alan (Nimbus) and last time our boat was lifted surprised to see our Prop anode missing likewise - unusual to completely go.

Had to try no less than five different anodes to find the correct one. Have taken careful note of the size for the next time to replace!

 

[PaulGooch]

After lifting my single engine boat a couple of weeks ago, I found the Volvo prop anode totally missing, which I believe isn't unusual.

When refitting a new one, I've been advised to use a small amount of Sikaflex on the threads, leaving sufficient thread clean for good anode to shaft contact...........does anyone else use this method?

I'm also thinking of adding a MG Duff shaft collar anode to supplement the Volvo one, (there isn't enough space to fit the MG Duff shaft anode with the steel insert)......my only concerns are how to ensure the anode remains tight on the shaft, and if it will cause any unwanted prop shaft vibrations.

Alternatively, I'm considering the MG Duff Electro Eliminator kit to fit inboard on the prop shaft, and connect this to my hull anode.

Any advice on either alternative would be greatly appreciated?

Many thanks,

Allan

I notice Alan said "prop" anode, but the majority of responses respond as if "shaft" anode.

We have the same make of boat as Alan (Nimbus) and last time our boat was lifted surprised to see our Prop anode missing likewise - unusual to completely go.

Had to try no less than five different anodes to find the correct one. Have taken careful note of the size for the next time to replace!

I read it as shaft anone, as per the thread title.

 

[VicS]

I read it as shaft anone, as per the thread title.

I think he initially refers to a prop anode. He says, "I found the Volvo prop anode totally missing"

He goes on to say, "When refitting a new one, I've been advised to use a small amount of Sikaflex on the threads, leaving sufficient thread clean for good anode to shaft contact
That can only refer to a prop anode screwed on to the threaded end of the shaft.


He then goes on to talk about shaft anodes, "I'm also thinking of adding a MG Duff shaft collar anode to supplement the Volvo one"

 

[PaulGooch]

I think he initially refers to a prop anode. He says, "I found the Volvo prop anode totally missing"

He goes on to say, "When refitting a new one, I've been advised to use a small amount of Sikaflex on the threads, leaving sufficient thread clean for good anode to shaft contact
That can only refer to a prop anode screwed on to the threaded end of the shaft.


He then goes on to talk about shaft anodes, "I'm also thinking of adding a MG Duff shaft collar anode to supplement the Volvo one"

I saw the first reference to "prop" anode Vic, but was more swayed by the "shaft" in the title and six references to "shaft" in the post

Not that it especially matters either way.

 

[AllanG]

The problem the OP has is that there is not enough exposed shaft to fit one of the larger, more secure shaft anodes, so his alternative to increase his anode "capacity" is a hull anode, probably with an eliminator for connection to the shaft - if he has room behind the coupling inside the boat.

Actually, I already have a 2kg hull anode, which is bonded to the engine, and a 'link wire' across my prop shaft flexible coupling. The prop shaft is then fitted with a small Volvo anode at the end of the shaft (behind the propeller), and it's this anode that 'disappeared'.

Allan

 

[DAKA]

Actually, I already have a 2kg hull anode, which is bonded to the engine, and a 'link wire' across my prop shaft flexible coupling. The prop shaft is then fitted with a small Volvo anode at the end of the shaft (behind the propeller), and it's this anode that 'disappeared'.

Allan

That is exactly as I read it Alan, end cone anodes.

The benefit is when it does come off no harm is done.

Unless someone has grounded your boat and had to buy new props and shafts and gone with cheap brass and cheap stainless 316 then you dont need shaft/prop anodes.

Bandit's boat above had issues but he is in guernsey which remarkably doesnt have a prop specialist on the island. At some stage a previous owner fitted a cheap brass prop that will suffer if not protected.

 

[Tranona]

Actually, I already have a 2kg hull anode, which is bonded to the engine, and a 'link wire' across my prop shaft flexible coupling. The prop shaft is then fitted with a small Volvo anode at the end of the shaft (behind the propeller), and it's this anode that 'disappeared'.

Allan

That will go first because it is small and closest to the item it is protecting. If the hull anode is close to the stern gear and properly bonded through the shaft then you probably don't need the one on the prop. Little point in trying to fit a shaft anode as that will only go the same way as the prop one and the hull anode will not be doing anything.

 

[n.herring]

If your props were subject to dezincification then they were poor quality, nothing to do with Hamble water vessel has rampant electrolitic issues.

Class 1 Nibrals will highly resistant to dezincification and other forms of corrosion.

Shaft anodes have their place with old fashoned bronze stern gear and slow shaft speeds.

Moden vessels have high shaft speeds and SHOULD have Nibral props. I pay a lot of attention to shaft diameter and strut design including machining a nice nylon fairing piece by leaving the cutless bearing proud of he strut. Having some goon putting a potential hand grenade on the shaft creating a complete mess of the laminar flow to the prop is simply brainless.

In addition to screwing up laminar flow as soon as anode suffers material loss you have out of balance force on the shafting leading to rumbling and potential hull damage.

Hi LS, I am sure you have a lot more knowledge of this than me and in theory maybe shaft anodes are surplas to requirements but you can not control the boat moored next to you or the electrics on the pontoon.

I have £2000 pounds worth of Nibril props as ornaments in my garden, boat was a broom 42, all electrically tested and bonded etc
Current boat is an Aquastar with Nibril props, Aquastar say use shaft anodes, the prop manufacturer who also make for Princess, Sunseeker etc say use shaft anodes. Clements who made the Broom props say use shaft anodes and both prop manufacturers say that the amount of contamination in the water and type of water you are in will effect dezincification.
So whilst I appreciate your comments on water flow etc nothing will convince me to risk another bill for 2k, Neil

 

[PaulGooch]

That will go first because it is small and closest to the item it is protecting. If the hull anode is close to the stern gear and properly bonded through the shaft then you probably don't need the one on the prop. Little point in trying to fit a shaft anode as that will only go the same way as the prop one and the hull anode will not be doing anything.

Exactly what mine would do.

When i first bought the boat it had no shaft or prop anodes, but had a hull anode. I fitted one the first year, as i thought the anode had probably just depleted, but it didn't last a season and the small hull anode was close to depletion. After giving it some careful thought, i realised that when i bought the boat the prop anode bolt was tight, so it hadn't depleted, it wasn't there to start with. I double checked that the coupling was solid, confirming that the shaft and prop were connected to the bonding circuit.

I left the prop nut anode off and fitted a much larger hull anode. No problems whatsoever and the hull anode is lasting well. The boat is 9 years old and has never had a shaft anode.

 

[Bandit]

I am somewhet suprised by Latestarters and Daka's comments above.

I had a problem with a pair of new props ( nickel, aluminium, bronze, (Nibral)) from a well known uk Manufactuer and shafts from the same manufacturer aqualloy 80.

According to the above posters I dont need any shaft anode or electro eliminator?

I put down the problem I had to poor connectivityaccross the R&D coupling, green connections on the shaft brushes or green wire ends ( not tinned at the time) and or no shaft anode.

After that fiasco I put new props from the same manufacturer with the same shafts, re wired electro eliminators replaced, an electrical bridge accross the R&D and shaft anodes and hey presto no further problems on that or further boats with the same set up?