Annode Corrosion

[olly_love]

We are having a lot of issues with corrosion on our Yanmar 2GMfw with a SD20 saildrive

We are getting through anodes ( prop and collar) in 2-3 months,

We have had the boat checked and no static earth issues,

So a random question,

Can a damaged alternator cause any issues when running? as we are trying to eliminate any issues that might be the running rather than static mooring

We are on a piled mooring and none of our neighbours are having issues

 

[QBhoy]

sorry to ask, but presumably thy are the correct anodes for your use ?
Other than that, is there any other metal fixtures near or around you boat that might be affecting them ?

 

[jwfrary]

Is the drive isolated from the engine in the same way as the volvo ones?

 

[roaringgirl]

Presumably the casing of your alternator is earthed to the engine. I can imagine an stray wire in an alternator causing a short to earth, which I think would affect your anodes.

I have been living on my boat for nearly 2 years now. The anodes were half gone when we unplugged and left Port Edgar marina in Edinburgh. I have only plugged in since for maybe 5 nights in total, and the anodes have not lost any noticeable amounts of material since.

 

[olly_love]

sorry to ask, but presumably thy are the correct anodes for your use ?
Other than that, is there any other metal fixtures near or around you boat that might be affecting them ?

Yep correct anodes,

and nothing else causing issues

 

[olly_love]

Is the drive isolated from the engine in the same way as the volvo ones?

Not too sure, We are heading down tonight to check it all

 

[vyv_cox]

Not too sure, We are heading down tonight to check it all

Yanmar saildrives are not isolated as Volvo ones are.
What other anodes are fitted to hull etc? Check for voltage between them and the saildrive. Is the paint on the saildrive in good condition? Does the prop have its own anode? If so, how well does it last?

 

[olly_love]

Yanmar saildrives are not isolated as Volvo ones are.
What other anodes are fitted to hull etc? Check for voltage between them and the saildrive. Is the paint on the saildrive in good condition? Does the prop have its own anode? If so, how well does it last?

No other anodes as we are a race boat,

currently the prop anodes and the saildrive one last 2-3 months max,
paint is new on the sail drive,

 

[Paul1962]

Can these anodes be supplied in magnesium ie for Fresh water instead of aluminium or zinc for Salt water?

If so, maybe you have magnesium anodes that will "fizz" well in salt water?

Just a thought

 

[vyv_cox]

Somehow it would seem that a potential exists between somewhere on the underwater surface e.g. keel, rudder, skin fittings? and the saildrive. It will be a very small voltage if the anodes last two months. Careful measurement should find it but isolating batteries will arrest it.

I seem to remember someone having a similar problem whose cause was an automatic bilge pump.