All Anodes have disappeared

[b_rodwell]

I have just hauled out my Lagoon 400 S2 after 15 months since the last slipping and anode replacement. The boat was mostly in the Med and and there was a mixture of at a marina and on the hook. There were almost no anode material left on the saildrives. I have had the boat for over 4 years and this has never happened before. As a consequence of having no anodes there was serious corrosion on both saildrive housings. Both need to be replaced at a cost of nearly Euro 9000.

Naturally I would like to avoid this happening again. Does anyone have any idea why the anodes would deteriorate so quickly?

Thanks

Brian

[a64pilot]

Based solely on the amount of money your having to spend and how vulnerable to corrosion saildrives are, I’d spend some more money and have a pro electrician look at it, hopefully you can find a certified corrosion analyst, if I’m using the term correctly.
Normally I’d say buy a reference electrode, Read up on it and tackle it yourself, but your already spending big bucks, maybe it’s time to go straight to a pro.
I’d still buy the reference electrode, learn to use it, and check myself every month or so to catch things before it gets too bad, after the Pro finds and fixes your problem.
You likely have some stray current. What has been installed of changed electrically during that time?
However the Pro will know what to check

[Vasco]

15 months is a long time without checking the anodes. I check mine every three months or so. The longest I've left without checking is about six months.

[Paul L]

Originally Posted by Vasco

15 months is a long time without checking the anodes. I check mine every three months or so. The longest I've left without checking is about six months.

The damage sux.
15 months is an unreasonable length of time to expect the zincs to last. We watch at 3 months and replace usually around 5 or 6. If the water is not conducive to getting into to check, then a silver-silver chloride half cell is pretty easy to use to determine the state of the zincs. They come with directions and require a quality digital volt meter to use.

[Scaramanga F25]

Saildrives...a mixed bag.

[Suijin]

If you're moving around, prior experience should not be counted on to estimate the life of your anodes. In marinas you may encounter stray current, you may be moving into water with higher salinity levels, etc. In short, the "wear rate" of your anodes can vary widely based on changing environmental conditions. Does not hurt to check your anodes every six months. If you have someone dive your boat, they'll check/replace them if you provide them with the right zincs.

I know a case where sail drives were turned into swiss cheese in less than two weeks from leaving a live wire in the bilge. At 18 months you probably are just looking at straightforward galvanic corrosion, it would not hurt to check your electrical system.

[Dulcesuenos]

In a hot marina our zincs last 3 to 4 months. At a friend's dock or not plugged into shore power they will last a year.

[sv Grateful]

All your zincs are belong to us.

[Rough Magic]

A diver to check at every three months (or sooner), and replace anything that looks less than 75% remaining. Learned the hard way on an outdrive.

[dfelsent]

Originally Posted by sv Grateful

All your zincs are belong to us.

I was sooo not expecting that!!

[Zhyachts]

Originally Posted by sv Grateful

All your zincs are belong to us.

I zinc he needs an isolation transformer.

[RaymondR]

As a former steel boat owner who experienced the odd corrosion problem I became aware of electronic devices which constantly monitored current flows in vulnerable underwater metal items and set of an alarm if the current flows were excessive or in the wrong direction.

You could solve the problem in that marina and have others in another marina. Unfortunately the alloys your sail drive leg is fabricated from are anodic to many other metals further down the galvanic series table and if there are unprotected steel piles in the marina and a return current path your saildrive legs may be acting as anodes to the marina piles or any other proximal more noble metals.

[Taswildlife]

Hi Brian
It sounds like your boat has probably developed a stray current issue. I have some experience with this having bought a steel hull in 2010 that had problems which are now fixed. Stray current is present when there is a positive or negative leak/connection from your battery to wet metal (submerged metal). This could be the entire boat in a steel or aluminium hull but can also be via your propeller in a GRP vessel or even through damp, salt water impregnated timber. If your vessel has even just a little then your boat is not isolated from the stray current effects from other "hot boats" is "contagious" when you are in a marina. When your boat is completely electrically isolated then it is immune to the cumulative effects of the boats around you. In marinas steel boats often wrongly take flack for this from uninformed boat owners that are looking for someone else to blame but I have worked on GRP vessels to electrically isolate them that were putting as much current into the water because their engine - reputed to be marinised - had a negative lead (from the battery) permanently connected to the engine. Nearly all commercial fishing boats and ships have electrically isolated engines (starter motors and alternators with two big leads) so I'm not sure why most recreational boat engines are not isolated. One problem here is that if your boat is in a marina in a line of other "hot boats" then each non-isolated boat thats added causes an accumulated effect, just like adding an extra plate in a battery. If your vessel is isolated then you are immune to these effects. Your engine is not the only place that stray current can come from. It can also be generated by changes in your domestic system or anywhere that electric current is present. Wiring and equipment can break down over time and begin transferring current especially where it is in a wet environment such as a wet bilge.
I was fortunate when my boat presented stray current issues to find an extremely sensitive electronic detector that can diagnose the source of the problem and allow the owner or marine electrician to resolve it. I had one permanently mounted on my vessel ever since that picks up problems as they happen. They are not inexpensive but work out a lot cheaper than having to fix the resulting corrosion. Anodes cannot overcome the effects of stray current which can be thousands of times stronger than the galvanic current generated by the union of dissimilar metals that anodes are installed to counter. Please don't let people tell you that you just need bigger or more anodes, they are wrong. The manufacturer of the detector I installed offered for me to be a distributor. I live in Queensland Australia but if you are interested in finding out more you can contact me at tim@solaexchange.com.au

[Bermuda Forte]

Following. Thanks

[mitiempo]

Originally Posted by Taswildlife

Hi Brian
It sounds like your boat has probably developed a stray current issue. I have some experience with this having bought a steel hull in 2010 that had problems which are now fixed. Stray current is present when there is a positive or negative leak/connection from your battery to wet metal (submerged metal). This could be the entire boat in a steel or aluminium hull but can also be via your propeller in a GRP vessel or even through damp, salt water impregnated timber. If your vessel has even just a little then your boat is not isolated from the stray current effects from other "hot boats" is "contagious" when you are in a marina. When your boat is completely electrically isolated then it is immune to the cumulative effects of the boats around you. In marinas steel boats often wrongly take flack for this from uninformed boat owners that are looking for someone else to blame but I have worked on GRP vessels to electrically isolate them that were putting as much current into the water because their engine - reputed to be marinised - had a negative lead (from the battery) permanently connected to the engine. Nearly all commercial fishing boats and ships have electrically isolated engines (starter motors and alternators with two big leads) so I'm not sure why most recreational boat engines are not isolated. One problem here is that if your boat is in a marina in a line of other "hot boats" then each non-isolated boat thats added causes an accumulated effect, just like adding an extra plate in a battery. If your vessel is isolated then you are immune to these effects. Your engine is not the only place that stray current can come from. It can also be generated by changes in your domestic system or anywhere that electric current is present. Wiring and equipment can break down over time and begin transferring current especially where it is in a wet environment such as a wet bilge.

There are several reasons that anodes can have a short life - 15 months is not a short life though.

First if you are using shore power in a marina you should have at a minimum a galvanic isolator. This eliminates or severely reduces the DC current from other boats on the same circuit or from bad marina wiring. Virtually all boats have the AC ground connected to the DC negative, either directly or through the chassis ground of a charger or inverter. This means that without a galvanic isolator all problems from others on the same circuit are also your problems. Even with the main AC switch off the ground is connected. Your anodes could well be protecting your neighbors boat. To go further an isolation transformer will totally eliminate any physical connection between your electrical system and that of others - heavier and more expensive but the ideal.

The other possible reason for short anode life could be an issue on your own boat. The most likely cause is an exposed wire in the bilge pump circuit as it is most often in water bit any wires in the bilge could be the problem.

On a boat that is not either steel or aluminum total isolation is not necessary.