Earthing sea cocks.

[moondancer]

On previous boats my sea-cocks have been connect to an 'earth' wire.

On my little twenty four footer, with no inboard engine, the sea-cocks are not connected to anything.

Should I be worried about electical type corrosion???

 

[PeterGibbs]

No. This idea is done to death. I suggest you leave the seacocks alone and they will be no trouble to you from galvanic corrosion

PWG

 

[pvb]

No, it's best not to connect them.

 

[moondancer]

thanks

 

[Refueler]

Exactly - isolated they have no continuity. Earth them and bingo stray currents... goodbye seacocks.

 

[vyv_cox]

Answers already given are accepted practice, but the assumption is made that the seacocks are made of some decent, corrosion resistant material. Old ones may well be tin-bronze, current Blakes ones and some others are DZR (dezincification resistant) bronze, which is actually a brass. In between old and current, thousands of skin fittings have been sold in brass, e.g. Tonval. These could already be in an advanced stage of corrosion.

I suggest you inspect closely and tap vigorously with a hammer to assure yourself that they remain secure.

 

[RichardTaylor]

On an engine sea cock that is that technically isolated using plastic piping, is it really isolated as there is sea water in that pipe which probably can conduct electricity from the engine?

 

[vyv_cox]

Yes. Seawater is not as great a conductor as many people think, and electric current likes to go in straight lines. The concept of using an anode outside the hull to protect an engine is flawed. It just doesn't happen.

 

[mixmaster]

Am I imagining it or is it far more common for boats in America to have their seacocks bonded?

 

[vyv_cox]

I've never been on an American boat, so I really couldn't say. Googling the topic seems to find plenty of USA sites giving advice that 'through-hulls' should be bonded. Current informed practice is that they are better left unbonded, as sometimes unexpected effects can result.

 

[MartinJ]

Don't be fooled by theory you can easily measure a voltage between skin fittings if they are connected & if you have any electrical equipment on the boat a hull anode is essential

 

[VicS]

[ QUOTE ]
if you have any electrical equipment on the boat a hull anode is essential


[/ QUOTE ]

Explain why that should be so please.
Properly installed electrical equipment should have no bearing on the matter.

My late friends boat had an inboard engine with presumably a manganese "bronze" prop on a stainless steel shaft, seacocks or skin fittings and gate valves which where probably bronze and cast iron keels.

No anodes were ever fitted and there was never any signs of corrosion that would have merited anodes in the 30 years he owned the boat. despite the fact that it had the electrical equipment fitted originally by Westerly plus a few extras he fitted himself over the years.

 

[VicMallows]

Purely observation on my 25yr old boat: (no shore power).

None of the seacocks are bonded to anything and all are in perfect condition.

P-bracket (also unbonded) suffered severe dezincification after 10 years. I HAVE bonded the replacement to nearby pear anode. So far so good.

Pear anode only replaced once 10 years ago. Current one about half wasted.

My conclusion is that composition of material in the fittings is the most significant factor. ?

Vic

 

[tabernacleman]

years ago after reading a yacht mag article on 'bonding' I realised that my ancient MacWester26 had no bonding whatsoever so I set about bonding all through hull fittings, engine, prop shaft etc, the following year the propeller disintergrated /forums/images/graemlins/laugh.gif
If it aint broke don't fix it is now my motto, and I know that a little knowledge can be expensive /forums/images/graemlins/confused.gif

 

[vyv_cox]

My boat is chock full of electrical equipment. I have no hull anode, removed it years ago. My seacocks are not bonded, neither is my P-bracket, although the latter is epoxy coated. I have a shaft anode and the prop has its own, but that's all. I check all underwater metal fitting regularly and there is no particular corrosion.

 

[swanny]

I can't get a decent grip of all this bonding stuff. Last winter I had a new engine fitted with all the trimmings! Engineer fitted a metal strop from shaft to engine over the flexible coupling. I told him the old flexible coupling was not bonded over and he replied, it definately should be! I took it off when he left. Nothing is bonded on the boat and now have a Kiwi Prop also so last season the shaft anode was almost perfect at the haul out. Do I need it with a stainless steel and plastic fan on the back??? Noone can tell me. Even had a Galvanic Isolater fitted five years ago but now I find out that due to no bonding it is actually doing nothing for me at all. Anyone want one??? I do have shore power, hot water tank, electronics etc but no corrosion. If it ain't broke...........!!!

 

[vyv_cox]

I totally agree with you. We are living in an era when there are so many people who can tell you the worst thing that might happen in theory, but have very little practical experience to decide whether it actually will.

There is a slight chance that the stainless steel propeller hub will form a galvanic couple with the stainless steel shaft and for the sake of looking at the anode every haul-out it might as well stay there.

I'm in a similar situation, as my Brunton's has its own anode and I don't see why I should need a shaft anode as well. I asked Brunton's at LIBS and they said 'Yes, you definitely need a shaft anode as well.' Why? it can't be protecting the shaft, with a bronze propeller, so what is it going to do? It has had the same shaft anode on for about five years now, with virtually no loss, whereas the prop anode needs to be changed every year.