Do i really need a prop shaft anode?

[Crinan12]

The MG Duff chunky ones last well. Fit two and they should easily last two years.

I only have room for a collar type one unfortunately

 

[Dogone]

There is no room on our shaft for one, so since 2008 there has never been a shaft anode. The rope cutter takes preference.

Just hauled out and done the underwater prep, bronze prop, S/S shaft, rope cutter and shaft all perfect. Not bad for 17 years with no shaft anode.

No prop anode either?

 

[oldgit]

Mobo on club pontoon moorings.
Annual lift for A/F and anode change.
2 x larger then required disc anodes on trim tabs,
1 x 4 kilo bar on Transom
2 x prop anodes.
2 x shaft anodes.

On last lift out after 12 months.
Trim tabs. 50% gone
4K Bar. 75% gone
Prop anodes. Both vanished inc bolts.
Shaft anodes. Not a trace of anodes or bolts.
Bowthruster . 90% left .OK for another year.

 

[vyv_cox]

Mobo on club pontoon moorings.
Annual lift for A/F and anode change.
2 x larger then required disc anodes on trim tabs,
1 x 4 kilo bar on Transom
2 x prop anodes.
2 x shaft anodes.

On last lift out after 12 months.
Trim tabs. 50% gone
4K Bar. 75% gone
Prop anodes. Both vanished inc bolts.
Shaft anodes. Not a trace of anodes or bolts.
Bowthruster . 90% left .OK for another year.

Do you use the two-hammer method of installing shaft anodes? In 40 years I have never lost one using this method

 

[Malish]

Mobo on club pontoon moorings.
Annual lift for A/F and anode change.
2 x larger then required disc anodes on trim tabs,
1 x 4 kilo bar on Transom
2 x prop anodes.
2 x shaft anodes.

On last lift out after 12 months.
Trim tabs. 50% gone
4K Bar. 75% gone
Prop anodes. Both vanished inc bolts.
Shaft anodes. Not a trace of anodes or bolts.
Bowthruster . 90% left .OK for another year.

Are you by chance connected to shore power for long periods?

 

[Rappey]

. What does the other anode do

Boat came with two... it used to eat both within a year. Once i took the boat out of the water and completely stripped and repainted the hull they now last over 4x longer. Ive heard if i paint the anodes they last even longer

 

[rotrax]

Do you have a hull anode? Shaft anodes are only one way of protecting the propeller, and mostly only relevant on boats with P brackets which have an exposed length of shaft where the anodes can be mounted. With "conventional" stern gear there is usually no real exposed shaft - just enough 15-20mm) to let water in and out. If a rope cutter is fitted there is still a need for this gap.

Of course, just changing that too. It is quite near the sterngear and this year when inspected it had lost material in a far more even way than before. I chose an aluminium anode last year instead of my usual MG Duff Zinc one. Well pleased. It was about 50% used up. And cheaper, although that was NOT the prime reason for choosing aluminium.

Not sure the 'gap' is just for letting water in and out - the shaft drives forward in ahead due to pressure from the prop. The gap is also required to allow for this fore and aft movement.

 

[Tranona]

Of course, just changing that too. It is quite near the sterngear and this year when inspected it had lost material in a far more even way than before. I chose an aluminium anode last year instead of my usual MG Duff Zinc one. Well pleased. It was about 50% used up. And cheaper, although that was NOT the prime reason for choosing aluminium.

Not sure the 'gap' is just for letting water in and out - the shaft drives forward in ahead due to pressure from the prop. The gap is also required to allow for this fore and aft movement.

Agreed about the fore and aft movement but that is relatively small, typically 2-3 mm, depending on the softness of the mounts (zero if an Aquadrive or similar is fitted). The primary purpose of the 15mm+ is for water flow.

 

[oldgit]

Do you use the two-hammer method of installing shaft anodes? In 40 years I have never lost one using this method

Yes. 2 x flogging hammers more usually used for driving in mooring pins.
Pretty certain they are eroding leading to their premature departure.
Last year the sad remnants of one shaft anode did remain with its securing bolts.
Yes , connected to shore power to top up batteries but we have a very posh isolator thingy installed from new.
To date always zinc.
As mostly brackish/salt water usually with only a week or two in non tidal will probably go aluminium next time ?

Must have got something right, a nice ring from all stern gear at the mo , in the dim and distance past hitting a prop blade has resulted in a dull thud and bits falling off, the going "pink" stage long past .