Saildrive Anode - Excessive Wastage

[goldentouch]

Advice welcomed please! Browsing through some of the posts on this forum, it seems that excessive anode consumption is not unusual to Volvo Saildrives.

I have a 130S saildrive with a volvo 3-bladed folding prop, and the 3-segment ring anode on the propellor hub seems to be consumed at an excessive rate - such that there is very little left after only 6 months in the water. The larger 2-segment anode on the saildrive is largely intact after a season in the water (15-20% wastage).

The propellor itself does not seem excessively corroded.

Is this something I need to be worried about? I have considered adding a separate over-the-side type anode bonded to battery -ve or the engine block, but from researching on this forum suspect that the propellor is isolated from this and don't think it'll do a lot of good. Tempted nonetheless for want of doing nothing else.

We do have a galvanic isolating transformer and the boat is kept on a swinging mooring, hence not often connected to shore power.

Any ideas, or has anyone experienced similar with a volvo folding propellor?

thanks for your help...

 

[Tranona]

Just a well known feature of that propeller. An anode over the side will not help as there is no way of bonding it to the prop. If its any consolation not all of them seem to eat the anodes but it is common. Other folding props such as the FlexoFold that I have do not seem to suffer in the same way.

BTW Welcome!

 

[tcm]

galvanic isolator is the answer - small lectrical unit that isolates your own boat from all the other stuff on the pontoon when hooked uo to shorepower long term. Less than £100

 

[fastjedi]

Same configuration (Volvo 3 blade + S130) Circa 6 months afloat well away from sources of electricity.
I change the propeller anodes every year (50% remaining) + change the saildrive anode after 3 years (75% remaining)
7 weeks in a marina at the end of last year finished our propeller anode and trashed the propeller.
We were not connected to shore power with the exception of a few weekends.

The hub is isolated from the saildrive shaft and dependant on the propeller anodes for protection.
Interestingly, the original volvo hubs (circa 10 years ago) were not isolated from the saildrive shaft and didn't have a slot for anodes.
I wonder if the change was made to cushdrive the hub given the weight of the propeller?

On the basis that the saildrive anode is mm's from the propeller and appears to offer no protection, I doubt anything will help significantly
I cannot afford to lose another propeller and face a year of diving to check on anode errosion

 

[Halcytwo]

Hi
I had exactly the same about 6 months out of a folding 3 blade prop on my sail drive.
Boat was fitted with a galvanic isolator too and the saildrive was isolated from the engine correctly.
I Think thats how its is !
Either get the snorker gear on in a quiet bay, or pay some divers to go down and change it for you mid year.

 

[vyv_cox]

galvanic isolator is the answer - small lectrical unit that isolates your own boat from all the other stuff on the pontoon when hooked uo to shorepower long term. Less than £100

Not applicable to a saildrive, I think. There should be no electrical connection between a saildrive and the rest of the boat.

 

[nigelmercier]

We do have a galvanic isolating transformer and the boat is kept on a swinging mooring, hence not often connected to shore power...

galvanic isolator is the answer - small lectrical unit that isolates your own boat from all the other stuff on the pontoon when hooked uo to shorepower long term. Less than £100

RTFOP And how would it help anyway, if the problem is only on one anode which is isolated?

There should be no electrical connection between a saildrive and the rest of the boat.

Or on some boats, the whole engine and the rest of the boat.

 

[mainsail1]

I am afraid your experience is the same as mine. I have found no way of limiting the damage.

Advice welcomed please! Browsing through some of the posts on this forum, it seems that excessive anode consumption is not unusual to Volvo Saildrives.

I have a 130S saildrive with a volvo 3-bladed folding prop, and the 3-segment ring anode on the propellor hub seems to be consumed at an excessive rate - such that there is very little left after only 6 months in the water. The larger 2-segment anode on the saildrive is largely intact after a season in the water (15-20% wastage).

The propellor itself does not seem excessively corroded.

Is this something I need to be worried about? I have considered adding a separate over-the-side type anode bonded to battery -ve or the engine block, but from researching on this forum suspect that the propellor is isolated from this and don't think it'll do a lot of good. Tempted nonetheless for want of doing nothing else.

We do have a galvanic isolating transformer and the boat is kept on a swinging mooring, hence not often connected to shore power.

Any ideas, or has anyone experienced similar with a volvo folding propellor?

thanks for your help...

 

[VicS]

I am afraid your experience is the same as mine. I have found no way of limiting the damage.

Unavoidable I think.

Stick a few bits of zinc on a copper alloy prop with quite a large surface area and the electrochemistry will make short work of the zinc.......... dissimilar metals and all that stuff.

 

[haydude]

galvanic isolator is the answer - small lectrical unit that isolates your own boat from all the other stuff on the pontoon when hooked uo to shorepower long term. Less than £100

I would recommend to document yourself before providing misleading advice. In this case the propeller is isolated, therefore a galvanic isolator has no effect, even if the boat were on shore power which is not.

 

[haydude]

I have the same propeller, same saildrive. The title should be propeller anode.
I found that once the propeller is coated in slime and lightly fouled the anode corrosion reduces. Next time is out of the water I will coat with prop-o-drev. So I have decided.

 

[fastjedi]

I have the same propeller, same saildrive. The title should be propeller anode.
I found that once the propeller is coated in slime and lightly fouled the anode corrosion reduces. Next time is out of the water I will coat with prop-o-drev. So I have decided.

Interesting .... I am following the same logic for this year without any real knowledge. I have spayed 90% of the hub and blades with Milldrive in the hope that less exposed surface area = less anode errosion. Anyone know if this is true?

 

[johnphilip]

Interesting .... I am following the same logic for this year without any real knowledge. I have spayed 90% of the hub and blades with Milldrive in the hope that less exposed surface area = less anode errosion. Anyone know if this is true?

That does seem to have helped for me, the anodes that I used to replace at mid season scrub now seem to stretch to a season. I know that the leg and prop anodes are independent but I found the leg anode did not erode at all and it was therefore on the boat for perhaps four years. It seemed totally inactive, I replaced it and this might be another factor in the improved life of the segmented anode,
The main problem is Volvo selling a few ounces of zinc formulated like a sugar lump for £££££...

 

[nigelmercier]

The main problem is Volvo selling a few ounces of zinc formulated like a sugar lump for £££££...

You could try casting your own, but do it outside as the fumes are toxic.

 

[VicS]

You could try casting your own, but do it outside as the fumes are toxic.

I think you will find that zinc fumes are only a problem during such operations as welding galvanised steel and casting brass . It should not be a problem if the metal is not heated excessively above its melting point.

Sound advice nevertheless to work outside.

Avoid over heating the zinc and take all the usual precautions for handing and casting molten metal

 

[richardbrennan]

I can also confirm that I suffer from the same problem. The boat is usually in the water for ten months and when it comes out the prop anodes have all but dissappeared. The only answer is, I think, to change them at the mid season scrub.

 

[VicS]

I can also confirm that I suffer from the same problem. The boat is usually in the water for ten months and when it comes out the prop anodes have all but dissappeared. The only answer is, I think, to change them at the mid season scrub.

It might just be worth tryin aluminium anodes if you can get them for the prop.

Some rough calculations suggest that aluminium anodes might last up to about a third longer than zinc ones. If that enables a full season of use it could be an attractive alternative to a mid season lift solely for changing anodes.

 

[TonyS]

My VP ring anodes used to disappear in 6 months as well. After 3 years I started polishing prop and then coating with a very thin coating of waterproof grease. The anodes are now only half worn after a year and there is a slight build up of scale on the prop blades. This scale is easily removed in a few minutes after lift out and re-polishing about 30 mins max. Have done that now for 7 seasons with repeatable results.

 

[Mrnotming]

Using the standard Volvo alloy 2 blade seems to result in slow anode erosion of the zinc anode.
However as soon as the black finish on the blades becomes compromised, the prop becomes "holier than thou" quite soon afterwards.Pitting and loss of material is extensive Holes through blades.I've bought a new prop and acquired another on ebay.However as the boat is dry sailed (the opposite scheme to Richard Brennan OP) the problem can be minimised.Cavitation caused by using max revs does more damage, though the pitch has been altered beneficially with the second prop, intercepting max torque at lower revs.The next spare is even coarser and may overwork the engine when its turn comes to be unboxed!Have to wait until I destroy the present object!