Shaft Anode Advice please

[dralex]

I am curious as the shaft drive on my boat has never had an anode on it since I bought it and there is now some electrolytic activity on the p bracket. Should I just fit an anode anyway and will it do any harm if there was never one there in the first place? I'm afraid I'm not very clued up on anodes.

thanks in advance.

Alex

 

[gianenrico]

An anode will eventually dissolve itself (like the Chesire cat) so if in doubt, You should not risk but the cost of the anode (if it disolves it means it was needed and you loose the worth of it, if it does not it means it was not needed and You keep the worth of the zinc.
Cheers,
Gianenrico
P.S.: I would not esitate in mounting the anode of appropriate size on the shaft

 

[andy_wilson]

Shaft Anode Advice

A shaft anode protects the the shaft, or more likely the propellor attached electrically to it.

P-Brackets are usually covered by a hull anode bolted on nearby, and connected electrically from the inside.

Your shaft will run in a shaft bearing that insulates it from the bracket, making a shaft anode useless for that purpose.

 

[dralex]

Re: Shaft Anode Advice

Thanks Andy- can you explain the hull anode in a bit more depth please and how would I go about fitting one if there is not one already there?

Thanks

 

[tome]

Re: Shaft Anode Advice

Alex

The shaft anode protects the shaft and propeller. On my Maxprop, there is an additional anode on the prop.

You need to get the right size by measuring your shaft diameter, then fit it close (about an inch gap) to the P braket to minimise vibration. Before fitting any anode, use a bit of emery to clean the surface to which you'll attach it so there's a really good electrical contact, and then do it up TIGHT.

Cheers
Tom

 

[KREW2]

Re: Shaft Anode Advice

Hi
The marine engineer who looks after my boat told me not to fit an anode on the shaft too close to the P bracket, he maintains it can restrict water flow through the cutlass bearing giving increased wear
KW

 

[KREW2]

Re: Shaft Anode Advice

Hi
I presume you wish to fit a pear shaped anode something I have just done with the guidance of my regular marine engineer. it is best located within 18" of what it is to protect, and you will need to get to the attachment bolts from the inside. When you have drilled the holes the bolts are secured and made water tight (I used Sikaflex). The protruding bolts on the inside then have to be earthed to the to the engine, if you can get it use tinned wire if not 2.5ml electric cable will do. Then go to outside bolts you are going to attach the anode to and use a multi meter to check the resistance between the outside bolts and your shaft. If you have done it right you will get a zero reading, once this is achieved fit the anode with the rubber backing pad, If I can do it anybody can good luck
KW

 

[tcm]

fit a galvanic isolator to reduce the eleectyrlytic effects of a wehole pontton being on the same earth circuit. Failrine do these for bigger boats, praps not yours. I used Steve of Sure Power to do this, may be able to find a number. £100 for GI, £100 fitting. When drying out, drill thru p-brackket and fit disk-type anodes that present small resistance, and mastic over the nuts to eliminate erosion onnem.

 

[tome]

Re: Shaft Anode Advice

Just checked the clearance between shaft anode and P bracket from a photo. Confirm it's about 1 inch, and was fitted by my marine engineer. No problems with cutlass bearing.

 

[KREW2]

Re: Shaft Anode Advice

Hi
Perhaps the engineer I use is a bit too fussy
KW

 

[tome]

Re: Shaft Anode Advice

Maybe KW. I can see his point but an inch seems ok for clearance. On a high speed craft you'd maybe want more, but I'm only guessing.

Cheers
Tom

 

[KREW2]

Re: Shaft Anode Advice

Hi Tom
I'm a bit like you, smile, nod in agreement, then pay the bill
Regards Keith

 

[Phoenix of Hamble]

A Galvanic Isolator is only needed if you are using shorepower that is also connected to your DC system... eg a shore power driven battery charger...