Bonding wire to anode.

[potentillaCO32]

I am re wiring my boat at the moment. Thanks to folk on here regarding wiring diagrams, VSRs and triple switches.

One question for the wise.

The boat had lots of things, including engine, connected the hull anode. It also had a feed from the starter battery negative to the same anode.

Should i just have a single connection from the gearbox/engine to the anode and forget connecting the battery negative. I have not seen this before.

 

[Alex_Blackwood]

I am re wiring my boat at the moment. Thanks to folk on here regarding wiring diagrams, VSRs and triple switches.

One question for the wise.

The boat had lots of things, including engine, connected the hull anode. It also had a feed from the starter battery negative to the same anode.

Should i just have a single connection from the gearbox/engine to the anode and forget connecting the battery negative. I have not seen this before.

Can I suggest more information please. Make, model and type of boat and is the present arrangement OEM?

 

[VicS]

I am re wiring my boat at the moment. Thanks to folk on here regarding wiring diagrams, VSRs and triple switches.

One question for the wise.

The boat had lots of things, including engine, connected the hull anode. It also had a feed from the starter battery negative to the same anode.

Should i just have a single connection from the gearbox/engine to the anode and forget connecting the battery negative. I have not seen this before.

The anode to engine/gearbox connection is to provide cathodic protection to the prop, if shaft driven, but that means any flexible shaft coupling must be bridged to complete the circuit,

If the engine block is the common negative for the engine circuits the battery negative will be also be automatically connected to the anode via the above .

If the engine has an isolated electrical system, i.e. engine block not used as common negative , there will be no connection between battery negative and the anode and you should not make one.
.

 

[potentillaCO32]

The anode to engine/gearbox connection is to provide cathodic protection to the prop, if shaft driven, but that means any flexible shaft coupling must be bridged to complete the circuit,

If the engine block is the common negative for the engine circuits the battery negative will be also be automatically connected to the anode via the above .

If the engine has an isolated electrical system, i.e. engine block not used as common negative , there will be no connection between battery negative and the anode and you should not make one.
.

Thanks Vic. The engine block is used as a common negative. There is a bridge across the driveshaft coupling. I'll just remake the block to anode connection and wont replicate the connection from the battery -ve.

 

[PaulRainbow]

The anode to engine/gearbox connection is to provide cathodic protection to the prop, if shaft driven, but that means any flexible shaft coupling must be bridged to complete the circuit,

That's one possible reason, but it is sometimes there to ground the DC negative.

If the engine block is the common negative for the engine circuits the battery negative will be also be automatically connected to the anode via the above .

If the engine has an isolated electrical system, i.e. engine block not used as common negative , there will be no connection between battery negative and the anode and you should not make one.
.

DC negative should be grounded. Best practice is to have all DC negatives connected to a central busbar, with a connection from the AC Earth circuit, then a single connection to the anode.

Just because the engine has a 2 wire isolated system does not mean it should not be part of this circuit. For instance, some sail drives are isolated from the engine, so the engine can potentially be grounded. If it's the whole engine/sail drive that's isolated you wouldn't make the connection.

 

[PaulRainbow]

Thanks Vic. The engine block is used as a common negative. There is a bridge across the driveshaft coupling. I'll just remake the block to anode connection and wont replicate the connection from the battery -ve.

In your case, others may differ:

All DC negatives should be connected to a common point, such as a busbar. Make a connection from here to the same bolt on the engine as the wire that goes to the anode. If you boat also have the AC Earth connected to the anode, connect that to the DC negative busbar. If AC Earth is grounded to the water you need a Galvanic isolator.