New prop, cathodic protection

[colhel]

I've just had a new prop delivered but before I fit it i thought I'd ask for advice on how best to protect it.
We bought the boat last year, a Nimbus 3003, single shaft and bronze prop. I noted that when we viewed her the hard an anode wasn't fitted (the trim tabs however each had one fitted). I asked for these to be replaced and a prop anode fitted prior to the sea trial as I didn't want to have to re-lift if all went well. Fast forward to launch day I noticed there was no anode on the prop or shaft, but the Brokers Engineer tried to reassure me that one wasn't needed, I thought this was rather odd but as there wasn't any evidence of one being fitted I reluctantly went ahead with the sea trial. In April I had a lift out for a wash off and noticed the prop was in pretty poor condition and hastily fitted a shaft anode in an attempt to stop it getting worse. I'm rambling...

So I've looked at pictures from when the boat was out of the water and can't see a tapped hole in the shaft to hold a cone anode, I don't want a shaft anode if I can help it. Is there another proven way of protecting my stern gear that wouldn't involve a shaft or cone anode ? A link to the trim tab anodes perhaps?

 

[omega2]

www.clementsmarine.co.uk will put you straight.

 

[andy59]

You need an electro eliminator kit from mg duff Colin , ( if you have space on the shaft before the gearbox flange ), this will also require a hull anode if not already fitted .
https://mgduff.co.uk/support/fitting-instructions/shaft-bonding

 

[colhel]

Brilliant Andy. Thank You.
Do you reckon I could connect it to a trim tab anode?

 

[rafiki_]

Colin, I have prop anodes on Rafiki, however these erode very rapidly so have fitted shaft anodes as well. This has worked well. What is your objection to the shaft anode?

 

[andy59]

We had shaft annodes on our old Sealine Paul, and found they could become loose towards the end of the season as they eroded. Princess have a perfect set up IMHO with two good size Hull annodes covering p brackets/ shafts and props . No issues in 4 years so far and dead easy to change at lift out :encouragement:

 

[colhel]

Colin, I have prop anodes on Rafiki, however these erode very rapidly so have fitted shaft anodes as well. This has worked well. What is your objection to the shaft anode?

Hi Paul.
Here's a picture of the anode when I fitted it in April, as you can see it's quite a lump and apart from the issue Andy as said about them coming loose, I'm also concerned it's disrupting the water flow as it goes through the prop making it less efficient.

 

[Portofino]

I wouldn’t worry about any performance issues re hydrodynamics being comprised by a shaft ( wrap round anode ) with your set up ..... Skeg, large rudder , lower rudder stay , distance of rudder from prop etc etc. All theses are far grater @ compromises then , then adding a shaft anode .
Any how here’s some pics of my set up fwiw .
Salient point ( I find myself having to spell things out theses days ) is the retaining nut is such designed to accept a tip anode .The hex at the tip is covered and the brass bit is where the tap is for the anode .So May be just change to prop retaining bolts ? Get away without tapping your existing prop shaft .
You could find a pair of theses prop bolts .











photo upload on web

 

[David435]

Colin, I have prop anodes on Rafiki, however these erode very rapidly so have fitted shaft anodes as well. This has worked well. What is your objection to the shaft anode?

Anodes work even longer if the boat is fitted with a galvanic isolator fitted at the point of entry for shore power.

 

[colhel]

I wouldn’t worry about any performance issues re hydrodynamics being comprised by a shaft ( wrap round anode ) with your set up ..... Skeg, large rudder , lower rudder stay , distance of rudder from prop etc etc. All theses are far grater @ compromises then , then adding a shaft anode .
Any how here’s some pics of my set up fwiw .
Salient point ( I find myself having to spell things out theses days ) is the retaining nut is such designed to accept a tip anode .The hex at the tip is covered and the brass bit is where the tap is for the anode .So May be just change to prop retaining bolts ? Get away without tapping your existing prop shaft .
You could find a pair of theses prop bolts .
]

Thanks for that, very useful.
Cheers

Anodes work even longer if the boat is fitted with a galvanic isolator fitted at the point of entry for shore power.

Thank You.

 

[rafiki_]

Hi Paul.
Here's a picture of the anode when I fitted it in April, as you can see it's quite a lump and apart from the issue Andy as said about them coming loose, I'm also concerned it's disrupting the water flow as it goes through the prop making it less efficient.

Shaft anode works fine there Colin. Will all the other sterngear the anode will not cause issues. Anode will only come loose if poorly fitted or when eroded so far there is no clamping load. Would not bother with prop nut anodes. Rafiki has these but they erode very quickly. Shaft anodes last much longer.
Fit a galvanic isolator. Mine is like this link. Just plugs in. No need for any substantive install.

https://www.ebay.co.uk/i/2931871669...MI5sPjpuex5AIVirHtCh3rsQQ5EAQYASABEgJPz_D_BwE