absence of shaft anode protection

[lindsay]

How long could you leave the propeller shaft of a 29 foot yacht in the water without direct anode protection, either end of shaft type or egg style? What is the worst that could happen and when does it start?

Long story I will not burden you with

 

[Mandarin331]

That depends on the boat and where you keep her. In a marina we launched in March,. By July the prop anode was a quarter gone. I suspect without it the equivalent would be missing from the propellor.

On a swinging mooring it would last longer,

 

[VicS]

How long could you leave the propeller shaft of a 29 foot yacht in the water without direct anode protection, either end of shaft type or egg style? What is the worst that could happen and when does it start?

Long story I will not burden you with

It depends on numerous factors not least on the alloys involved. The answer could be almost indefinitely.

It's folding props made from a mix of alloys where the anode becomes important.

If you fit an anode on the shaft adjacent to a bronze, or other copper alloy, prop it will be consumed fairly rapidly whether or not it is actually doing anything useful. That's the electrochemistry between the two dissimilar metals at work.
A hull anode bonded to the shaft and prop will probably last longer simply because it is further away.

If you are concerned that your "long story" hides some exceptional circumstances then by all means fit an anode. Shaft or hull mounted is your choice but it would be very exceptional circumstances indeed that would make this urgent

 

[rotrax]

Our current boat has no prop shaft anode, and never has.
There is no room between the cutlass and rope cutter.
The bronze prop cleans up like new and the shaft is fine.
The boat was launched in 2008 and does have an OE galvanic isolator.

 

[PaulRainbow]

Our current boat has no prop shaft anode, and never has.
There is no room between the cutlass and rope cutter.
The bronze prop cleans up like new and the shaft is fine.
The boat was launched in 2008 and does have an OE galvanic isolator.

Almost the same as mine, except mine was launched in 1980 and does not have a GI, shore power and 12v are isolated.

My previous boat had plenty of exposed shaft and a large four blade prop. As Vic said, a prop anode or shaft anode disappeared quickly. As the shaft was fitted directly to the gearbox (no flexy joint) it was bonded to the hull anode, so i left the prop and shaft anodes off. Never had a problem and the boat was always connected to shore power.

 

[CAPTAIN FANTASTIC]

I have never fitted an anode on the engine or shaft; the prop shaft is stainless steel and the propeller is large three blade bronze. Every year I anti foul the propeller; never had any issues. As others have stated, it all depends on a number of things; in many cases, the anode provides no protection, it just gets consumed because is there.