Good or Bad: Electro Eliminator for Shaft

[Lucas Gan]

Just viewed a Fairline boat in the nearby marina. I saw the shafts have electro eliminators on them. The problem is the eliminators wear the two shafts around 1-2mm depth scratches, so making a huge groove on the shaft. Is it worth it to have that eliminator on shafts? I don't feel good about the groove on the shaft. What do you think? Thank you.

I forget to take a photo. The thing is similar to the picture shown below.

 

[Tranona]

They are essential on that installation as they are there to electrically bond the tull anodes to the shaft/propeller assembly to protect the propeller from dezincification. The groove on the shaft is unlikely to have any detrimental effect on the shaft.

 

[Hurricane]

They are essential on that installation as they are there to electrically bond the tull anodes to the shaft/propeller assembly to protect the propeller from dezincification. The groove on the shaft is unlikely to have any detrimental effect on the shaft.

Absolutely 100% agreed.

 

[PCUK]

Something wrong with the installation you saw. Mine never wore the shaft and never should unless the carbons have worn away and it is metal to metal.

 

[andy59]

Something wrong with the installation you saw. Mine never wore the shaft and never should unless the carbons have worn away and it is metal to metal.

Just what I was thinking, Rioja has over 600 hours clocked up and no groove on the shafts just a shiny stripe .

 

[superheat6k]

I fitted these to Boadicea and never so much as a scratch just a shiny band. A light squirt of WD40 occasionally and sometimes the carbons require a clean, especially if any seawater gets on the brushes.

 

[BartW]

in my boat, the shaft is mechanically connected with the gearbox, and that is fixed on the engine, which is connected to the boats grounding
so therefor the boat does not need such a device.

 

[Tranona]

The boat in question has flexible couplings which make bonding through the engine/gearbox problematic.

 

[Plum]

in my boat, the shaft is mechanically connected with the gearbox, and that is fixed on the engine, which is connected to the boats grounding
so therefor the boat does not need such a device.

I have that arrangement too but the electrical resistance from gearbox to shaft is excessively high so had to fit a Electro Eliminator.

www.solocoastalsailing.co.uk

 

[BartW]

I have that arrangement too but the electrical resistance from gearbox to shaft is excessively high so had to fit a Electro Eliminator.

www.solocoastalsailing.co.uk

ok,
its the first time I ever heard about such a device,
but every day is a learning day

 

[Hurricane]

ok,
its the first time I ever heard about such a device,
but every day is a learning day

Princess fit them as standard.
We also had ones fitted to our Sealine
I think they are regarded as the correct way to protect your props from galvanic corrosion.

 

[Tranona]

Yes they are if you are not able to get a good circuit through the gearbox coupling. On smaller hp engines R&D do a bridging strap that bridges the flexible bit of the coupling and this seems to work OK, but maybe not with the size of couplings, shafts and props etc on your kind of boat. Space is often a problem on smaller boats as well.

 

[JOHNPEET]

Does having anodes mounted on the shafts negate the need for these?

 

[BartW]

Does having anodes mounted on the shafts negate the need for these?

NO !
such a device assures that the props and or shafts are connected to the boats ground, so that the anodes can do their work correctly

 

[Tranona]

Does having anodes mounted on the shafts negate the need for these?

Yes, shaft anodes (and propeller nut anodes) are an alternative to a hull anode bonded electrically to the shaft. However the downside is sometimes getting enough bulk to last a season between lifts and the possible effect on performance on a high speed boat.

The key things the achieve when deciding on a system are that the thing you are trying to protect (in this case the propeller) has to be electrically connected to the sacrificial anode, close by underwater and in "line of sight". Shaft anodes meet this easily if properly installed, but hull mounted anodes have to be placed close to the propeller and electrically connected through the shaft. The first is normally not a problem but the second often is, hence this discussion on the alternative methods.

 

[JOHNPEET]

Yes, shaft anodes (and propeller nut anodes) are an alternative to a hull anode bonded electrically to the shaft. However the downside is sometimes getting enough bulk to last a season between lifts and the possible effect on performance on a high speed boat.

The key things the achieve when deciding on a system are that the thing you are trying to protect (in this case the propeller) has to be electrically connected to the sacrificial anode, close by underwater and in "line of sight". Shaft anodes meet this easily if properly installed, but hull mounted anodes have to be placed close to the propeller and electrically connected through the shaft. The first is normally not a problem but the second often is, hence this discussion on the alternative methods.

Ok. I have a steel boat and have spent many hours researching the various opinions and books on how to protect the steel hull from corrosion and maintain electrical safety whilst on the water. So my approach is as follows: I have 12kg of zinc bolted across the underside of the hull which is evenly divided between 6 locations. I also have 1kg on each rudder and 250g on each shaft.

The DC systems all have separate negative returns including the engines. The AC earth is bonded to the negative bus and the negative bus is bonded to the steel hull in a single location only. The single hull bond prevents circulating currents through the steel, provides an easy point for disconnection for testing to ensure that a neg to hull fault has not occurred and ensures that any fault to the steel hull on the AC side is cleared by the RCDs . The shore earth and boat earth is separated through an isolation transformer.



Im hoping that this is all adequate without fitting the shaft brushes?If I did fit them, the only place they could be connected to would be either the neg bus or the hull.

Thinking about it - the metal of the engines and gearboxes are not connected to the neg or hull.

 

[BartW]

Ok. I have a steel boat and have spent many hours researching the various opinions and books on how to protect the steel hull from corrosion and maintain electrical safety whilst on the water. So my approach is as follows: I have 12kg of zinc bolted across the underside of the hull which is evenly divided between 6 locations. I also have 1kg on each rudder and 250g on each shaft.

The DC systems all have separate negative returns including the engines. The AC earth is bonded to the negative bus and the negative bus is bonded to the steel hull in a single location only. The single hull bond prevents circulating currents through the steel, provides an easy point for disconnection for testing to ensure that a neg to hull fault has not occurred and ensures that any fault to the steel hull on the AC side is cleared by the RCDs . The shore earth and boat earth is separated through an isolation transformer.



Im hoping that this is all adequate without fitting the shaft brushes?If I did fit them, the only place they could be connected to would be either the neg bus or the hull.

Thinking about it - the metal of the engines and gearboxes are not connected to the neg or hull.

don't have experience nor knowledge about steel boats, so I can't give accurate advice,
but regarding your last sentence,;
usually the engine gets its neg connection from the starter and or alternator wiring,

 

[JOHNPEET]

don't have experience nor knowledge about steel boats, so I can't give accurate advice,
but regarding your last sentence,;
usually the engine gets its neg connection from the starter and or alternator wiring,

Not in my case. My starter motors and alternators have isolated negative returns.

 

[Tranona]

Im hoping that this is all adequate without fitting the shaft brushes?If I did fit them, the only place they could be connected to would be either the neg bus or the hull.

The brushes are only a means to connect the anode to the shaft/prop assembly. The galvanic action will be between the shaft and the prop and it is the zinc in the prop that will be depleted. Your shaft anodes will be "sacrificial", being depleted instead of the zinc in the prop. The only question is how long they will last and you will only find this out when you put the boat in the water. This is all completely separate from your hull system.

 

[JOHNPEET]

The brushes are only a means to connect the anode to the shaft/prop assembly. The galvanic action will be between the shaft and the prop and it is the zinc in the prop that will be depleted. Your shaft anodes will be "sacrificial", being depleted instead of the zinc in the prop. The only question is how long they will last and you will only find this out when you put the boat in the water. This is all completely separate from your hull system.

Mmmm, think I will look at putting some additional zinc on the nuts.