Anodes on Sterndrives - normal to change every two months?

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acbruce

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HELP

I have a Fairline Targa 34 (2005) and am having problems with the sacrificial anodes on the sterndrives (Volvo KAD 300s). These were changed in August and have now completely dissappeared after only three months. Fortunately the boat was coming out so no damage done. However three months (almost exactly) does seem very fast.

Yes it is on a marina (Swanwick) and on shore power and has stainless steel props but three months to a very dangerous condition. At this rate I will have to have the boat lifted every two months next year. /forums/images/graemlins/mad.gif

Volvo are suggesting active anodes at £600, but I am finding it hard to believe that this is normal wear rate.

Does anyone have experience with these engines etc?

Does anyone know of an engineer who I can ask to test the boat and or my berth?
 
That seems excessive, even with SS props.

I'd get an electrician on board and check for earth leakage before anything else. Active anodes would prob sort out the symptoms, but the cause needs sorting.
 
Hi

I've got a targa 34 with the KAD 300s. My stearn anodes last just touching 6months.

I've just replaced them with the legs in the beach position and lying on the swim platform.

Low water where I am is only 2metres so if I dropped something I could always hook it out.

Why not beach the boat and change the anodes between the tides?

Im also planning to add extra anodes on the legs so that when the legs are trimmed to beach position. I will be able to change the anodes without removing the props.

Cliff
 
Good evening,

I had similar problems with both a Sessa 36 (KAD44) and a Targa 40 (KAD300). On the Sessa there was an earth leak and I got a shock from the props!! – Luckily I had taken the boat out of the water to install a bowthruster or the drives might have disappeared. On the Targa 40, the anodes completely went in 5 months, I had extra anodes placed all over the sterndrives and this made a huge difference - the issue is caused by the dissimilar metals of the drive and SS props. The active anode was not available at the time (I had it on a Mercruiser years before) but it sounds a good idea.

-Andrew
 
I have found that fitting a galvanic isolator to my Targa 37 (kad44's, stainless props) has significantly slowed the rate at which the anodes are being used. Definitely worth installing if you haven't already got one; not expensive, easy to do.

Cheers
Jimmy
 
Jimmy

The local boat yard I use suggested I should fit galvanic isolators. Ive just done a google search and there is a good selection to choose from.

Which one did you fit?

Cheers
Cliff
 
I just fitted a galvanic isolator on Friday and aluminium anodes last week.

I am now hoping the anodes will last longer than the previous 6 months. I know they can, as the previous owner last changed them in Nov 04. They were not bad when I changed them in April 06, what happened between then and now may have been more boats coming back into the marina from storage ashore with bad earths.

I agree the isolator is easy to fit.

D
 
Ive had an isoltor fitted since the boat was delivered.
still got the same alu anodes and looks like they would go for another year...tho i shall change them in the spring..as a precaustion.
boat= 18 months old.
 
I've got Kad 300's, with S/Steel props. I understand it's the S/steel that causes the problem of excessive anode erosion. Volvo recommend an extra "mushroom" anode to be fitted on each leg, which was done to mine, BUT I also strongly recommend a galvanic isloator to be fitted to the mains inlet. With this, and the additional anodes fitted too, it seems to cure the problem. Mine were fitted early August, and I reckon the anodes are about 20% gone, so they should last the year.

For sure, 2 months is not acceptable!!
 
My Sunseeker used to eat ring anodes within 8 weeks (Kad 42s with ss props) I started to turn the mains off whenever I left the boat and bolted anodes to the cavitation plate and doubled up the transom shield anodes. They lasted a season after that.
 
I had an S37 with KAD44s with SS props just downriver at Universal. Same problem.

I had doubled-up transom anodes, four hook-up fork anodes and modified transom anodes fitted just above the props, a galvanic isolator and I was on a pontoon with no power.

I even tried hanging a large lump pf zinc, grounded to the engines, between the outdrives, but it made no difference.

The prop anodes completely disappeared in about 10-12 weeks.

In the end, I just got it lifted and held over lunch break while I changed the prop anodes. It takes about 30 minutes to change both. A bit of a pain, but in the overall cost of boating, not that expensive.

It is a well-known problem with SS props.
 
Similar problem over here...

Aluminium props, anodes completely gone after 9 months and some damage to the props done.

Underway of tracing any leakage in the AC and/or DC circuits, check if groundings are properly installed and plan to
1. add a transom shield anode (not already done by previous owner) ,
2. wire all groundings to a central grounding plate and the pre-mentioned anode

Is it normal for a 32ft boat with normal use of AC circuit to need replacement of sacrifical anodes every 4-6 months?
Has anyone taken the above steps to help me about what to expect?
Is there anything i should have in mind?

(BTW Nigel Calder's Boatowner's Mechanical and electrical manual is great!)
 
I knew of a chap that had excessive anode wear so he decided he'd hang an anode in the water by the drives as he'd seen others do.

So he bought a big anode and carefully lowered it into the water and positioned it at the correct height by the drives.

Doubt it helped much though, he'd tied the anode onto a piece of string!!! /forums/images/graemlins/grin.gif

I suspect he'd not fully grasped the concept somehow...
 
[ QUOTE ]
So he bought a big anode and carefully lowered it into the water and positioned it at the correct height by the drives.

Doubt it helped much though, he'd tied the anode onto a piece of string!!! /forums/images/graemlins/grin.gif


[/ QUOTE ]

Been there done that (not the string connection thingy obviously /forums/images/graemlins/laugh.gif) but not much help indeed...
 
Thanks very much for all your comments so far. Obviouosly not an isolated problem and I will investigate a Active Corrosion Protection System from VP. Also get the boats grounding etc tested and whether there is a galvanic isolator already installed or not.

An airberth is starting to look more attractive!!
 
I've got the GI70 from Safeshore marine.

The galvanic isolator is basically just a couple of diodes in a heatsink, so the easy way to test is to put a multimeter across the earth of your shorepower inlet on the back of the boat to an earth in one of your sockets in the cabin.

My £5 multimeter from maplin has a diode check function and this shows the voltage drop (about a volt) across the galvanic isolator.

If you don't have the diode check function, the other way to check it is to use the resistance setting of your meter - a reading of zero indicates no isolator, a reading of not zero indicates that one has been installed.

Remember to unplug your shorepower first before doing any of this...

Cheers
Jimmy
 
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