Electrolysis Damage to Prop - advice please

[bobgarrett]

I have a bronze prop on a Volvo saildrive. Until last season the anodes on the prop have never eroded completely, the prop has had some encrustation on it easily scraped off and then polished so the prop looks great.
At the end of last season on lift out we found the anodes completely gone and some areas of the prop have been etched so the surface cannot be made to shine as easily (the areas where the encrustation was presumably most thin).

So to my questions.
I am planning (and have started) polishing up the prop using fine wet-and-dry, then steel wool and then polish in the hope I can get a good surface again. Is that the right thing?

Why might my anodes have eroded so much faster; maybe due to sailing in different areas or maybe just a faulty marina supply? And how do I ensure against this in future; is a galvanic isolator the answer?

Thanks, for any input.

 

[VicS]

You dont say which engine and gear box combination.

Many VP installations have the gear box electrically isolated from the engine ....... something to check if applicable.

Others have an engine installation isolated from the DC negative , often with an earthing relay or solenoid which comes into operation during preheating, starting and stopping . All things to check where applicable.

A GI is usually a good idea if connected to shorepower for prolonged periods but the above should avoid the problems you are encountering .

Important to look at this alongside any alterations and new equipment you may have added.

Your problem is confined to the prop and its anode is it? No accelerated loss of sail drive leg anode? Thats serious when that happens because the sail drive leg can corrode vey quickly once its anode has gone.

 

[bobgarrett]

It is a Volvo D1-30 which I believe has saildrive isolated from engine. I will check this isolation.
The saildrive appears fine and the anode on it is almost complete.
So the problem appears only to be the prop.