anode.jpg
This is the anode that should be on the motor...with earth lead attached to.
anode.jpg
This is the anode that should be on the motor...with earth lead attached to.
Gotta Love Maroochydore.
i think those anodes are simply doing their job, like has been said though, check that your motor is properly bonded to your hull and also check that your electrical system is completely isolated from your hull. remember that you will normally get a small electric corrosion cell where the stainless bolts hit the alloy transom bracket (dissimilar metals) and this will corrode even better when it's all left in salt water.
with your electrics, the thing to avoid is any component of your electrical system using the electrolyte (sea water) as a return path to the negative terminal so you want all electrics isolated completely from the hull and you want a good return path from the motor block to the negative terminal using a cable/bond (this cable/bond is there anyway for outboards with an electric starter).
My bolding.Originally Posted by gazza2006au
Am I reading that correctly ? If I am, that doesnt sound right ? ? As others have pointed out, you dont want any electrical connection to your hull at all. The earth/ NEG, on the battery is the earth for EVERYTHING. Every light etc needs a neg wire to a neg bus bar. Unlike your car where the chasis is good for an earth/neg connection.
i agree lancair, if this is an electrical earth then i'd be a bit suss
Gidday Gazza
Here is a pic of an anode (since been replaced on last service) mounted directly underneath my outboard, the cable is not an electrical cable as such.
I'm assuming it's an earthing cable from the base of the anode and fixed to a point beside the hydraulic ram which you unfortunately can't see in the pic.
One of your pics show's two bolt heads sticking down where the anode used to be?
It appears corrosion is attacking the base of your outboard & surrounds because there is no anode in that area.
Hope this is of some help?
100_2228.jpg
LITTLE SKIPPER!
This pics suggest the stainless bolts are causing the corrosion. Remove them and cover them in duralac.
Correct me if I'm wrong but isn't stainless steel not supposed to corrode? Refit a new anode with earthing cable Gazza?
Lancair/Paddles, I don't think there would be a negative grounded inside the controller but even if there was then it wouldn't make any difference.
The only return path to the battery negative would still be via the main engine negative lead, not the hull. No different to the steering helm being grounded at the dash & also at the engine tiller via the steering cables.
The thing to be wary of is grounding the hull to the battery negative other than via the engine block main negative.
The pic suggests to me that the engine is dissolving because the sacrificial anode is missing.
Trying to isolate the motor from the hull via the bolts is counter productive because it would negate any protection the hull can get from the engine anodes.
You haven't hooked up a Furuno earth stud have you Gazza?
Stainless corrodes, but that is beside the point. In the picture, the corrosion is galvanic corrosion of the aluminium caused by the stainless bolts. Isolate the stainless bolts from the aluminium and you will stop that particular problem.
24 years, no Duralac, no corrosion, no worries.
It's all in the anodes and it's best to securely bond your hull to your motor via the bolts.
corrosion.jpg
that's right fed, bonding is the key. the anode sacrifices itself to protect any metallic structure bonded to it so the secret is to make sure that everything in the electrolyte that you want to protect is bonded to the anode somehow.
an electrical fault/leak will create another seperate corrosion cell where a return path is created through the electrolyte (sea water) and your hull becomes the anode, it doesn't matter if there is another earth cable going back to the negative terminal the return through the electrolyte just tries to return to the negative terminal via this new parallel path.
the stainless bolt into an alloy bracket creates yet another seperate corrosion cell due to the dissimilar metals like andy has said. i'm not too sure whether the outboard anode can actually prevent this cell from functioning, but if you do decide to isolate the bolts from the transom bracket then you need to make sure the outboard is bonded to the hull with another seperate earth strap.
hey fed, that piccy is a classic example for us all of your cathodic protection working perfectly.
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