saildrive anode lost

[mowa]

Around four weeks ago I discovered that I had lost the Saildrive anode, there was considerable fouling in the area so the lost must have happened some time before. The previous summer was in place. Because the delay in the shipyard: vacations, bad weather, etc. I still have not been able to hang out the boat to install the anode.  I am thinking in do not wait any longer and contract a to diver to install the anode instead. How critical can be a Saildirve without anode?. Should I hurry up?

[geoff]

I would not wait, the consequences of galvanic corrosion of the alloy leg would be very expensive compared to the cost of a diver. Geoff

[Symphony]

Essential you replace as soon as possible. if you have a one piece anode on a 120 leg then the prop has to come ff first so not so easy to do underwater. Later 130/150 legs with 2 piece anodes are easier.

[dawntreader]

.......(as above) and switch batteries off and disconnect from shore power when not using boat in meantime

[tckearney]

anybody advise if hanging an old anode over the side on a steel wire attached to the sail drive.  Would this help?  I note a few fibre glass boats at our marina have this.  I know its common for metal boats. 

[dawntreader]

anybody advise if hanging an old anode over the side on a steel wire attached to the sail drive.  Would this help?  I note a few fibre glass boats at our marina have this.  I know its common for metal boats.

A key part of the above is 'attached to the saildrive'. It would also need to be part of the the overall 'galvanic circuit' so would need to be near the source of the other 'electrode'. Given that it would be 'hanging over the side' I doubt it would make much difference (even if it showed signs of corrosion over time).

Better still: I  had a galvanic isolator fitted shortly after getting the boat and have only changed my anodes once since 2006 and have no corrosion on the propeller/saildrive.

[Jeffatoms]

Depending on the model of the saildrive you have, it may not be replaceable by a diver as the prop may have to be removed (risky!)  Best to do on the hard and at the same time do a complete flush of the saildrive lubricant.  The 130 allows partial oil change from within the boat but Volvo still recommends complete change from below every three years.  Oil change on the 120 must be performed out of the water.

[Symphony]

anybody advise if hanging an old anode over the side on a steel wire attached to the sail drive.  Would this help?  I note a few fibre glass boats at our marina have this.  I know its common for metal boats.

Yes, that can be effective but you need to ensure that it is attached to the gearbox/saildrive after the connection to the engine as the engine is electrically isolated from the transmission. Not easy to arrange on a temporary basis, but some people have made a permanent installation with a wire to a through deck fitting that allows the hanging anode to be connected when needed. This can be useful for those who move their boats to and from salt to fresh water so that they use alternate zinc or magnesium as appropriate. Important the hanging anode is positioned alongside where the saildrive is and sufficiently deep so that it is "sight" of the housing.

A temporary set up may be useful in the OPs situation until he can fit an anode.

BTW the material of  the hull is irrelevant as a hanging anode is specific to protecting stern gear and is useful if the normal anode erodes quickly and there is no room to fit a larger anode on the shaft or prop. A saildrive is different  as the anode is protecting the aluminium housing, not the prop, but the principle of increasing anode capacity by using a properly bonded hanging anode is sound. anode wear on the 120 leg can be rapid, although usually at least a season before replacing. The 130 anode has more than twice the bulk so lasts much longer.

[mowa]

Finally, the anode is in place without too much damage, it seems, in the leg...

[tckearney]

Thank you  Symphony very informative.   I fitted a Bronze auto prop on my Bavaria and last year and was shocked how quickly the Saildrive anode and the prop anode(the prop has its own anode)  eroded.   When I had the aluminium prop the anode lasted  several years.   I will be leaving the boat in the water this year and flying off to the sunshine for four months, so the boat will be pretty much unattended.   Would hanging an anode over as close to the saildrive as possible help ?  Are there any risks that you can think of. 

[Symphony]

Yes, a hanging anode would help. You can get them from MG Duff and you will need to work out a way of bonding the anode to the gearbox casing.

Fitting a bronze prop should not affect the saildrive anode as the prop should be electrically isolated from the saildrive. The anode on the prop is necessary because there are stainless steel components in it. Anode erosion on folding and feathering props varies enormously and some makes are notorious for high erosion rates whereas others (like the FlexoFold I have) erode very slowly - in fact the 2 blade I have does not have any anodes and is now in its 8th year of being in the water all year round. Later models of the same make do have anodes but they are very small and from what I hear erode very slowly.

[JEN-et-ROSS]

About 10 years ago I was concerned about the saildrive anode, so I fitted a large 'teardrop' anode externally in addition to the saildrives' own anode and bonded it to the saildrive casing using a heavy cable.
Same idea as a 'hanging' anode but it's effective 24/7.......Bill

[tckearney]

Symphony (anybody)  I do not quite get the “ should be electrically isolated from the saildrive”   Maybe I should not have fitted this Prop.  The Prop is Bronze with some stainless Steel bits by way of bearings and securing screws.  However it slides straight on to the splined drive shaft from the saildrive.  There does not appear to be any isolating material between the prop and the saildrive, as there is with the original Bavaria aluminium prop.  The saildrive anode was virtually completely eroded after 15 months and little use.  I did not think that Bronze and aluminium had a high dissimilar metal potential difference.   Although I am in a marina I very seldom leave the mains connected.    I'll phone Bruntons later today for an explanation

[tckearney]

just had a reply from Bruntons.   For any other owners that have a bruntons prop see atatched and you can clearly see the black insulating washer that insulates the saildrive shaft from the propeller.  Bruntons have informed me that it is a volvo requirement that their props are insulated from the drive shaft