Cretin of the century award - runaway winner. Or can you beat this?

prv said:
I've not come across that (not surprising, as I've only been on one American boat and I wasn't digging around in the bilges).

I can't really fathom what it's meant to achieve.

Do you know why they do it?
Click to expand...

To speed up galvanic corrosion and thereby sell more skin fittings and/or boats.
 
Some years ago now, a surveyor asked for a "sample fastener" to be withdrawn from each seacock and inspected. I thought that was one of the most sensible suggestions I've ever had from a surveyor! It's something I've done each season since. I've never found a problem with the seacock fasteners, but I did nearly lose the rudder once because a previous owner had cut the rudder shaft and welded two flanges to the ends so that the rudder could be taken off without digging a hole under the boat. unfortunately, he'd used A2 stainless bolts to hold the flanges together and they had suffered (extreme) corrosion in the area covered by the flanges and (I assumed) deprived of oxygen. One bolt had sheared, and the other three were waisted quite extensively.
 
To bond or not to bond, a question often asked but I have yet to find a solution.
My Westerly Storm has a bond on the "P" bracket and a bond on the engine raw water inlet, which looks like an add on.
The heads has a blakes seacock, which is original. It must have leaked at some stage and was virtually covered in epoxy, so much so it looked like a meringue. I had the boatyard remove, and service it, and as far as I can see it is not bonded.
I am loathed to remove the bonding for the raw water inlet for the engine in case it has been replaced with a new inferior type of seacock.
How can I tell if this is the case.
 
Tranona said:
Electrolysis is the fear. But this occurs where there are two dissimilar metals in contact in an electrolyte (seawater). This can either be two components (shaft and prop for example) or an alloy of two different metal (plain brass, which is copper and zinc). These conditions do not exists with bronze seacocks such as yours unless it is connected through other metal, for example with a copper pipe to the engine. The material is chosen specifically because it is resistant to corrosion in seawater. So why connect it to other metals or to the battery? As others have said there are thousands of boats using that type of seacock without any bonding and suffer no ill effects. Have a look on the MG Duff site. They are the experts and make money out of selling anodes and they do not recommend bonding skin fittings and seacocks.
Click to expand...

Point taken, but my post suggested safety when hooked up to shore power, which I now believe to be the reason.

My boat, in her 15th year, only has a prop anode, which lasts at least two seasons. It has a factory fitted galvanic isolator. All the high quality bronze skin fittings and sea cocks appear visually perfect, when inspected annually externally, and far more frequently when we are sailing.

M G Duff are certainly world leaders in their field. The builders of American boats have some experience in their job also.

Not many fit fittings not fit for purpose as is happening with European craft...........................................
 
rotrax said:
Not many fit fittings not fit for purpose as is happening with European craft...........................................
Click to expand...

But that is not relevant to the OPs situation as he seems to have Blakes seacocks.

BTW not convinced wiring brass fittings to an anode will be effective as the anode has to "see" the metal it is protecting and that is difficult with the number and disposition of fittings on a typical modern boat.
 
I'm following the discussions here, and sort of understand the reasoning for not bonding. As I've seen before on the fora there are two points of view, and both are tenaciously held by their proponents.

So, to try to make it possible to sleep at night, does bonding cause a problem and should my new bonding wires be removed for fear of corrosion/wasting?
If it doesn't cause a problem, then I'll leave them all on.

Or.............................?

Many thanks for all your responses.

RW
 
Robert Wilson said:
I'm following the discussions here, and sort of understand the reasoning for not bonding. As I've seen before on the fora there are two points of view, and both are tenaciously held by their proponents.

So, to try to make it possible to sleep at night, does bonding cause a problem and should my new bonding wires be removed for fear of corrosion/wasting?
If it doesn't cause a problem, then I'll leave them all on.

Or.............................?

Many thanks for all your responses.

RW
Click to expand...

You need to find what they are bonded to. If to a hull anode then nothing is likely to happen. Would not be happy having them bonded to anything electrical or the engine. There really is no need for bonding. My Blakes type seacocks are 50 years old and no sign of corrosion.

Your prop and shaft may well benefit from an anode, but even then on many older boats this is not necessary either.
 
Tranona said:
You need to find what they are bonded to. If to a hull anode then nothing is likely to happen. Would not be happy having them bonded to anything electrical or the engine. There really is no need for bonding. My Blakes type seacocks are 50 years old and no sign of corrosion.

Your prop and shaft may well benefit from an anode, but even then on many older boats this is not necessary either.
Click to expand...

Very interesting. I shall discuss with "the man with the pliers and wire" in the morning. I think all are bonded to the hull anode, but I seem to recollect that there is a wire onto an engine mount as well.

Time for bed, said Zebbedee :encouragement:
 
Tranona said:
As others have said there are thousands of boats using that type of seacock without any bonding and suffer no ill effects. Have a look on the MG Duff site. They are the experts and make money out of selling anodes and they do not recommend bonding skin fittings and seacocks.
Click to expand...

And yet MG Duff also state that "Bronze and Stainless Steel Rudders, Rudder Hangings and Shaft Brackets should also be bonded to the main anodes" - http://www.mgduff.co.uk/pdfs/Fitting_Instructions.pdf.

If a rudder and its fittings are all bronze - why include them in the system...?

And while we're on that page, why include the engine and gearbox in the system - if the engine marinizing components also include their own zincs?
 
Last edited:
MYStargazer said:
And while we're on that page, why include the engine and gearbox in the system - if the engine marinizing components also include their own zincs?
Click to expand...

Because how else would you connect the hull anode to the prop and shaft?

The engine is just being used as a conductive lump of metal, it's not being protected itself.

Pete
 
vyv_cox said:
Every explanation begins with words like 'metals in seawater corrode from the moment they are first immersed'.
Click to expand...

I have selected this short bit of Vyv's post for a reason.

First Mate and I recently visited the Mary Rose Museum.

The bronze cannons recovered from the seabed where they had lay for almost 500 years show no significant corrosion.

Whatever the truth of it is, the skin fittings, sea cocks, prop and shaft show no corrosion or galvanic action on our American boat which are bonded to the battery.

The physical evidence shows that IF the theory is wrong, in practice it works OK.

That will do for me.
 
prv said:
Because how else would you connect the hull anode to the prop and shaft?

The engine is just being used as a conductive lump of metal, it's not being protected itself.

Pete
Click to expand...

http://www.mgduff.co.uk/pdfs/Fitting_Instructions.pdf

I understand why there's a lead running from the shaft to the anode - this is protecting the prop and shaft.

But I'm confused as to why there's then a second lead running from the shaft to the engine... what is this achieving?
 
ripvan1 said:
Interesting thread and now for possibly the daftest question ever posted - If fittings can be bonded to a battery anode, why are zinc anodes placed on the exterior where they can't be seen?

I'm expecting a really obvious answer - (it's an age thing)
Click to expand...

Obviously a stupid question. Please put my mind at rest someone
 
The American position on bonding is led by the ABYC. They support the bond and protect approach because it gives greater lightning protection and provides better radio grounds as well as protection against stray current corrosion inside the hull. However they make a specific point of stating that through-hulls need not be bonded. (ABYC standard E-2, I believe)
 
ripvan1 said:
Interesting thread and now for possibly the daftest question ever posted - If fittings can be bonded to a battery anode, why are zinc anodes placed on the exterior where they can't be seen?

I'm expecting a really obvious answer - (it's an age thing)
Click to expand...

Not sure I understand your question. What is a battery anode? Where bonding is used it is normal to ground everything to either the engine or the battery negative (which are normally in electrical contact anyway) to prevent the possibility of different potentials between them. Exterior zinc anodes are then supposed to protect the skin fittings and maybe other things such as rudder fittings, P-bracket, etc. but need to be in line of sight with all of them to do so. An exterior anode cannot protect an engine.
 
Salty John said:
The American position on bonding is led by the ABYC. They support the bond and protect approach because it gives greater lightning protection and provides better radio grounds as well as protection against stray current corrosion inside the hull. However they make a specific point of stating that through-hulls need not be bonded. (ABYC standard E-2, I believe)
Click to expand...

That's a good explanation. Don't suppose you have a link to the ABYC standard?
 
I have just lifted my boat out of the water and found that the anode material had significantly reduced since the same time last year and the remaining zinc is a soft paste rather than the hard metal of any previous years. The anode is near the stern and connected to the stern tube and the engine. Any thoughts? The batteries had been removed from the boat over the winter other than one which was used to pump the bilges by connecting a crocodile clip to switch it on.
 
myquest said:
I have just lifted my boat out of the water and found that the anode material had significantly reduced since the same time last year and the remaining zinc is a soft paste rather than the hard metal of any previous years. The anode is near the stern and connected to the stern tube and the engine. Any thoughts? The batteries had been removed from the boat over the winter other than one which was used to pump the bilges by connecting a crocodile clip to switch it on.
Click to expand...

I suspect it means that it has been working, saving your prop and shaft, assuming there is a direct electrical connection between them and the engine, from corroding. The finger anodes in my Bukh engine were often soft and spongy when I replaced them.
 
You must log in or register to reply here.

Share this page

Top