Wiring anode

[Plymade]

Is it necessary to wire the anode to the keel? The reason I ask is
that I have a zinc anode connected to the engine & the prop but not
the keel. When I put a volt meter from the keel bolt to the engine I
got a smal reading, about .5volt!

 

[AIDY]

hey there a chap on the other forum with the same problem.... could ask him /forums/images/graemlins/grin.gif

 

[steve_cronin]

That\'s called a voltaic cell

Why is it happening?

Could be just dis-similar metals in which case you need bonding between everything (all metal hull fittings) which is short linked to a hull anode.

Or it could be a leakage from shore power or pontoon supply - in which case you need bonding between everything (all metal hull fittings) which is short linked to a hull anode.

However, because the causes can be complex, perhaps the best remedy is to give the keel it's own dedicated anode NOT connected to the rest of the protection system. If you have a saildrive, this needs it's own anode IN NO WAY connected to any other piece of metal tyhan the drive in contact with sea water.

Steve Cronin

 

[VicS]

1. An anode must be resonably close to the item(s) it is to protect and it should be "within line of sight" of it or "be able to see it. That does not have to be taken too literally but it means that it must not be screened from it.

2. It must have a good low resistance electrical connection to it. MG Duff recommend 4mm² pvc insulated and stranded copper cable! If the stern gear is to be protected by a hull anode then in addition to a connection to the gearbox or engine block connection to the prop shaft should be made via a "brush".

If you want protect your keel a single small anode located near the stern gear is unlikely to be effective. You will need larger anodes nearer to the keel, or even on the keel, and one located either side to satisfy the "must be able to see" rule if you are to protect both sides. A large keel may well need more than one electrode either side.

If however you have no corrosion problem with the keel leave well alone.

Theoretically there is no need to connect the keel system to the sterngear system but if you have shorepower it should be and it should all be earthed to the shorepower earth. (if shorepower is left connected, then a galvanic isolator will probably be needed in the shorepower earth connection)

You will find info on the MG Duff website at www.mgduff.com

 

[boatmike]

Quite normal. It aint broke so don't mend it.