Shaft Annode Position ?

andy59

andy59

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Boat is coming out in a couple of weeks for the usual maintenence jobs , one of them being replacing the shaft annodes . They were fitted by previous owner just in front of the P brackets and i am wondering if it would make any difference if they were fitted up by the hull partially in the recess of the stern tube ( maybe less turbulence over prop ? ) , or should i just not bother as there is good continuity between shaft and hull annode ?
Thanks for your wisdom in advance :)
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Are sure you need them at all.
After taking advice from this forum and researching.
I checked the quality of my props and shafts and took mine off.
Worried for a year until lift out but found my props and shafts were fine.

It is complicated and you need to check what your shafts and props are made of but the electrical qualities of my props and shafts were well within limits.

It's not like the old days when you had steel shafts and brass props.
 
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Thanks Daka , i looked around the yard and not many mobos seem to have them and there are 6mm bonding wires attached to everything insidethe boat . The reason i am not sure is that previous owner replaced props , but couldnt find out if it was damage or dezincification .
 
I know what you mean about turbulence - however, it remains to be proved whether re-sting them will reduce drag. Yours is a Fairline? Try contacting them to see how it would have been when it left the factory.

Our shaft anodes are conical in shape and fitted on the shaft end over the prop locking nut. But it's not a Fairline.
 
Thanks Graham , Its actually a sealine F36 but i know what you mean about the annodes on the end of the shaft nut , i have just seen on MG Duffs site that they have bought out a new range of shaft nut annodes so i`ll give them a ring tomorrow .
 
Mine has prop nut anodes - but I don't trust them not to fall off as they melt away - happened twice before. I also use two per shaft - ball anodes (like yours) and have done so for about 4 years now and always place them at the prop end as its mainly the props I want to protect. They make no difference to performance as far as I can tell and the props are still going fine (and these are french ones!). I replace them every year and they are about 30-40% gone. Mind you my prop shafts are not bonded so do need good protection externally.
 
Two points.

First, I'd always fit them 'just in case'. The cost of replacing props is expensive - the cost of anodes isn't. I fit mine about 3' in front of the P bracket.

Second, to preserve the flow of water through the cutlass (lack of water flow = premature wear) fit the anode a good couple of feet away from it. In your case I'd fit it even further fwd as you suggested.

Happy cruising!
 
Belt and Braces

You generally dont know shaft brushes have a connectivity problem until after you have severe prop erosion (going pink or going carotty). The first thing to be affected is the prop nut then the prop then the shaft.

I always use brushes and shaft anodes.

I fit them about halfway between P bracket and sterngland.

I always put a jubilee clip tight above and below the anode on the shaft with the tail of the clip trailing when the engine is running ahead to stop the anode riding up or down the shaft, I have seen both the anode damahing the hull and stopping water flow to the P bracket cutless.

As Piers says shaft anodes are not expensive compared with props.
 
DAKA said:
Are sure you need them at all.
After taking advice from this forum and researching.
I checked the quality of my props and shafts and took mine off.
Worried for a year until lift out but found my props and shafts were fine.

It is complicated and you need to check what your shafts and props are made of but the electrical qualities of my props and shafts were well within limits.

It's not like the old days when you had steel shafts and brass props.
Click to expand...

Spot on!!

Upside, as much use as rubber eye........

Middle ground view anything which affects laminar water flow costs you.

Downside IF they are working depletion causes shaft imbalance and I have known them come apart and grenade the hull.

Pointless
 
Latestarter1 said:
Spot on!!

Upside, as much use as rubber eye........

Middle ground view anything which affects laminar water flow costs you.

Downside IF they are working depletion causes shaft imbalance and I have known them come apart and grenade the hull.

Pointless
Click to expand...

Agree, motor bikes and ashtrays come to mind.
 
Thanks for the replies everyone , I am not going to replace them but if i can get the correct size prop nut annode i will try those for a season and see if they are actually needed . BTW does anyone know the thread size on a 45mm sealine shaft ?
 
FWIW I put on shaft anodes last year for peace of mind. I thought I heard a slight grumble coming from the back of the boat and the shaft anodes sprung to mind. Had they slipped up or down the shaft? Would that cause damage? Being the paranoid type of persion......

I have an underwater camera so stuck that under for a good old inspection. One anode was fine the other was gone! Vanished. In future I think they might be more bother than they are worth.
 
asteven221 said:
I have an underwater camera so stuck that under for a good old inspection. One anode was fine the other was gone! Vanished. In future I think they might be more bother than they are worth.
Click to expand...

thats exactly what happened to me several times, even paid a diver to take them off once.

just because they waste away doesnt mean they are doing anything.

My shaft is Tmet
my prop is bronze alloy although forget which exactly.

the two metals are almost the same electrically.

adding an anode reacts a new electrical current between the shaf/prop and the zinc anode where there is a huge electrical difference.

Its like adding a battery under your boat that only creates water disturbance and risks getting wedged in your cutlass bearing.

check what sealine used for your shaft
check what your prop is made of

90% sure you dont need to fix a zinc battery to your shafts but you may have a steel shaft and a brass prop so best check first.
 
The trick I was recently told was to fill the recess where the fixings are with silicone to preserve this area from eroding and therefore losing their grip on the shaft. I have done it this year for the first time so cannot comment on its effectiveness but it seemed to make sense.
 
Years ago I learned the hard way, shaft brush connected all ok at the start of season, brushes intact and in place, all wiring looked ok. continuity proven.

Next lift a holey propeller highly corroded new prop required.

Traced back to a broken wire on the shaft brush.

An expensive lesson for the sake of belt and braces.
 
I could be way off here Bandit but as far as I am aware Guernsey doesnt have a prop specialist.

Do you know the type of material your wasted prop was made of and shaft composition.



I replied to Andy only after recognising a reasonably modern tunnel and british boat builder known for reasonable quality, fair assumption he has quality shafts and Bronze alloy props to match electronically .
 
This was 10 years ago, new shaft and props from a very reputable supplier in uk Aqualloy 30 shafts props standard mix and it was only on one side, the other side was fine.
 
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