When should a sacrificial anode be changed?

[Telo]

When should a sacrificial anode be changed? Ours still has its basic shape, a bit pitted, but still has plenty of surface area. Yet, I've seen people to replace them at about that stage.

Also, any suggested uses for the old one?

[Mark]

Also, any suggested uses for the old one?

Melt it with a blowlamp to make the next one!

[aquaplane]

I would have thought that if they last 5 years you replace them when they get to 25% left, ie before it won't last 'till next time you check + a bit for safety.

Some folk make anodes from zinc from a model shop mostly used anodes would work just as well as there is likely to be a good weight left to melt down. My dad managed to make some engine anodes in the garage using a primus and an old cast iron pan. I think he used zinc out of a jar but an old anode could be recycled.

[Aja]

When should a sacrificial anode be changed? Ours still has its basic shape, a bit pitted, but still has plenty of surface area. Yet, I've seen people to replace them at about that stage.

Also, any suggested uses for the old one?

Donald

Weight is the key. If you can weigh a new one and can get your existing one off without damage weigh it. I would replace when it is 25% of the new one.

With pitted anodes it is too much guesswork to gauge how much active material is actually left.

Regards
Donald

[Pete Cooper]

When should a sacrificial anode be changed?

It's usually easiest when the boat is out of the water.

[Caer Urfa]

When should a sacrificial anode be changed? Ours still has its basic shape, a bit pitted, but still has plenty of surface area. Yet, I've seen people to replace them at about that stage.
Also, any suggested uses for the old one?

You do not say how long the existing one has been 'on' !

When inspecting boats it's surprising just how many anodes are not correctly wired up,(some not even wired at all).
Anode wear can also depends on the water quality where you are, I 'lift out' every two years and by then up here on the North East coast mine is about 50% worn, so I just replace it complete.

Most boats also have two anodes, sometimes externaly but sometimes some engines have special shaped engine anodes fitted.

The most common problem I find is if the boat has a 'pear shaped' anode wired to the stern tube mounting and another wire to say the engine block and the shaft has a flexable coupling, some have no 'jump wire' linking the two shaft coupling flanges either side of the nylon coupling, as if there is no wire then the anode has not got a circuit.

Hope this might help
Mike