Anode life

[fontmell]

Hi
I have Volvo penta 120s saildrive and question if there is a way of extending the saildrive anode life which is between 6 months for zinc and slightly longer for aluminium For example if I added a pear shaped anode to the hull above prop connected to saildrive . I ave galv. Isolator and don’t leave boat ‘plugged in’
Thanks

 

[MontyMariner]

Move to a swinging mooring!
Marinas are a hotbed of stray currents.

 

[vyv_cox]

Volvo saildrives are isolated from the rest of the boat, so a hull anode will do nothing. A hanging anode with the conductor connected to the saildrive inside the boat could prove beneficial. Ensure that the cable is well insulated and protected from chafe.

Otherwise your only option is to reduce the cathode area by painting but I assume the SD is already painted.

 

[VicS]

Volvo saildrives are isolated from the rest of the boat, so a hull anode will do nothing. A hanging anode with the conductor connected to the saildrive inside the boat could prove beneficial. Ensure that the cable is well insulated and protected from chafe.

Otherwise your only option is to reduce the cathode area by painting but I assume the SD is already painted.

Most, but not all, VP sail drives are isolated ... It depends on the engine. IIRC isolation was introduced with the B version of MD2010/20/30/40 engines in about 1994
MD22 series are a notable exception though.

A dedicated hull anode can be bonded to an isolated sail drive in that same way as a hanging anode but you'd have to be wary of a back-water electrician using it as a grounding point for the shorepower earth . I doubt if it will extend the life of the sail drive anode unless very close but it would serve as back up if the main anode became completely depleted.

 

[Sandy]

Hi
I have Volvo penta 120s saildrive and question if there is a way of extending the saildrive anode life which is between 6 months for zinc and slightly longer for aluminium For example if I added a pear shaped anode to the hull above prop connected to saildrive . I ave galv. Isolator and don’t leave boat ‘plugged in’
Thanks

To simply answer your question: Remove the vessel from salt water or adding more mass to the anode.

Why do you want to extend the life? Will you be away from the boat for some time?

 

[VicS]

Hi
I have Volvo penta 120s saildrive and question if there is a way of extending the saildrive anode life which is between 6 months for zinc and slightly longer for aluminium For example if I added a pear shaped anode to the hull above prop connected to saildrive . I ave galv. Isolator and don’t leave boat ‘plugged in’
Thanks

Generally people get longer than 6 months for sail drive leg anodes ( prop anodes are a different matter) May be you should look for reasons for it being so short. Isolation bridged perhaps if yours is an isolated one.

 

[Daydream believer]

What prop do you have & do you have an ambassador stripper? This may connect the prop to the saildrive (it does with my Brunton) & may have an effect on the anode wear

 

[vyv_cox]

Most, but not all, VP sail drives are isolated ... It depends on the engine. IIRC isolation was introduced with the B version of MD2010/20/30/40 engines in about 1994
MD22 series are a notable exception though.

Ok if you want to be pedantic. Those manufactured in the past 28 years

 

[Fontmell1]

Hi many thanks all the above responses to my question

I reply as follows

Engine is a c therefore isolated
I believe a bonded anode connected to the gear box which is not isolated from the sail drive but is isolated from engine is the same as hanging an anode over the side and connecting to gearbox - am I correct
Prop is flex o fold 2 blade folder and fitted with ambassador stripper. I hear what you say about continuity between prop and sail drive but I don’t understand why stripper would be sold to be fitted to V Penta sail drives if acts as conductor. I have no continuity between engine and sail drive
I want longer life because boat in use 12 months a year and in Solent only 1 lift per year or 18 months means a substantial cost saving compared to 2 per year as at present

My feeling is to fit pear abode above prop and bond to gearbox unless anyone can good reason not to
Thanks your interest

 

[Tranona]

I am surprised your anode life is so short. I had exactly the same setup for 12 years with a Bavaria 37, 10 in the Med and 2 in the UK in a marina in Poole. Changed the anode 3 times in Greece, last one just before we left Greece. That last one was still fine after 2 years in the water in Poole.

You are right the Stripper should not affect the anode life. The anode is to protect the aluminium from any stainless components. The anode is bolted to the unpainted aluminium of the outer seal housing which has stainless fastenings plus of course all the internals of the drivee are stainless.

Adding a hull anode bonded to the drive inside will do little to increase the life of the saildrive anode, because that will go first being in direct contact with the aluminium. A remote hull anode relies on the circuit being complete through the water which is less effective than direct contact. So effectively it will only come into play when the drive anode has gone. There may be some "sharing" but probably not enough to make any real difference until the anode is gone.

Worth trying though and mount the hull anode as close as possible to the drive. Think of it more as a backup rather than increasing the life of the main anode.

 

[Ammonite]

When it comes to the Ambassador rope cutter and continuity between the propellor and the saildrive it depends what prop you have. If your prop is isolated from the saildrive by design like the Bruntons autoprop, which has a central rubber bush, the Ambassador will bridge the isolation. If the prop wasn't isolated in the first place fitting the Ambassador won't make any difference.