Prop' anode after 6month in the water.

[Ian_Edwards]

I've been checking the Max Prop today.
I was surprised by how much of the anode has disappeared.
The anode also has a very uneven surface, almost volcanic, which is unusual.
There's an additional collar anode on the shaft, touching the boss of the prop'. That has some wear, but it's much more even, typical of what I've seen over the years.
Was this anode made out of particularly impure bit of zinc, or is there something else I'm missing?

 

[Tranona]

Looks normal to me, although 6 months is a bit short. Photo shows 2 anodes from my Featherstream, the one on the right about 9 months and on the left about 5 months.

Since then I have painted the prop and added a hull anode bonded to the shaft and it seems to have reduced the wastage significantly. Your shaft anode will probably not do much until the cone anode has gone as the latter is closer to where the mixed metals (stainless and bronze are. also the electrical contact will be better with the screws into the hub clamping the mating faces. Have you left enough clearance between the shaft anode and the stern tube? should be minimum 15mm to let water flow in and out.

 

[lustyd]

Seems very worn for 6 months to me, but the wear it expected and intentional. You're actually lucky the bolt holes didn't wear first and drop the cone off which often happens as they're the closest to the prop.
I wouldn't be too worried but I would certainly be investigating causes of the excessive wear just in case there is an issue.

 

[Ian_Edwards]

Thanks for the replies.
A few extra bits of information.
The boat is kept on a mooring, and I anchor most of the time. I only had 6 nights in a marina in 2024.
The boat has a thrust bearing just after of the gearbox, so there is very little axial movements in the shaft.
The stern tube is feed with pressurised water, from the raw water cooling system to ensure the cutlass bearing is lubricated and cooled. There's a gap between the rope stripper and the end of the cutlass bearing, but not as big as one would normally need.
I had a pm about internal stray currents, which is possible. The seacocks are Marelon, with the exception of the engine raw water inlet.
There also a large anode bonded to the engine block.
And finally this much worse than previous years.
Interesting to hear that the degree of consumption of the anode is seen to be near normal, and I do paint the holes with a spot of antifouling paint, to stop the anode from falling off too quickly.

 

[lustyd]

You paint with AF? That could be your problem you’re adding (probably) copper in the AF.

 

[Tranona]

Thanks for the replies.
A few extra bits of information.
The boat is kept on a mooring, and I anchor most of the time. I only had 6 nights in a marina in 2024.
The boat has a thrust bearing just after of the gearbox, so there is very little axial movements in the shaft.
The stern tube is feed with pressurised water, from the raw water cooling system to ensure the cutlass bearing is lubricated and cooled. There's a gap between the rope stripper and the end of the cutlass bearing, but not as big as one would normally need.
I had a pm about internal stray currents, which is possible. The seacocks are Marelon, with the exception of the engine raw water inlet.
There also a large anode bonded to the engine block.
And finally this much worse than previous years.
Interesting to hear that the degree of consumption of the anode is seen to be near normal, and I do paint the holes with a spot of antifouling paint, to stop the anode from falling off too quickly.

The hull anode is probably not doing anything unless there is continuity to the shaft past the thrust block and it is less than 1m in direct line to the prop. It will even then not do anything until the two anodes closer have gone. Seacocks are irrelevant in relation to what goes on in the prop. The galvanic action is between the bronze hub and blades and the stainless gear and the cone anode is introduced into the circuit by being bolted to the hub. The shaft anode is secondary as it is also in contact with the hub, but it is worth checking continuity. Stray currents are electrolysis rather than galvanic and you should not have any on a mooring nor in a normal marina berth. My boat spends 52 weeks a year in a marina berth with intermittent shorepower. The anodes for the propeller are the normal cone and now a hull anode bonded with an electroeliminator on the shaft. Painting the hub and blades to reduce the exposed area seems effective in minimising galvanic action. I used PropODeV in these photos but it did not last well so will bite the bullet and use Velox before next season,