Through hull anode bolts

[Tinto]

Hi
I have an anode under my my aft cabin which

a) isn’t connected to anything

and

b) is weeping water through it’s fixing bolts

I have had a look at the manual
And can’t find a wiring schematic for anodes. There is one immediately beside it which is wired up. Wondering if
I should connect them up together?

Starlight 39.
The manual says the bolt for the anode is fixed to the hull. Are these not usually fixed in place with sikaflex or are some cast into the fibreglass?

 

[Pye_End]

2 anodes next to each other? Photos?

Probably through bolt - Sikaflex to seal. Sounds as though yours needs re-bedding, but need to get to the bottom of what it is supposed to be attached to!

 

[lustyd]

Could it be that it's a pair of bolts for a pear anode and somone fitted two smaller ones?

 

[VicS]

If its not connected to anything it is not serving any useful purpose.

Take it off and make good the holes Or refit and connect the two together.

What's the other one connected to / supposed to be protecting?

Anodes are usually fitted using special studs with a welded on square plate, not bolts.
See this video. You see the studs after 1 minute 10 seconds but its worth watching the whole video.

 

[Tranona]

Hi
I have an anode under my my aft cabin which

a) isn’t connected to anything

and

b) is weeping water through it’s fixing bolts

I have had a look at the manual
And can’t find a wiring schematic for anodes. There is one immediately beside it which is wired up. Wondering if
I should connect them up together?

Starlight 39.
The manual says the bolt for the anode is fixed to the hull. Are these not usually fixed in place with sikaflex or are some cast into the fibreglass?

The most you need is an anode to protect the prop and this is usually a hull anode wired to the gearbox/engine and then to the shaft. If you have a flexible coupling there should be a bridge across it to complete the circuit. The only other reason for having a second hull anode is for an earth for the shorepower, but this is not common on olderboats. If you have a feathering or folding prop this will also have an anode to protect the yellow metal from the stainless bits in the mechanism. If you have this you may find the hull anode does not do much.

So remove the second redundant anode and glass the holes over.

 

[vyv_cox]

If it is like the one that was on my Sadler 34 (in the same place) it is wired to the P-bracket. This seems to be a misunderstanding on the part of Sadler/Starlight, as it can fulfill no useful purpose. I took mine off and filled in the holes when I first bought the boat almost 30 years ago.

Painting the P-bracket offers far better protection, plus anodes on the prop and shaft.

 

[johnlilley]

You don't say whether the hull is grp or wood. If wood then consider not connecting the anode up to anything as anodes fitted to timber hulls are very destructive to the hull if they are wired to the structure.
John Lilley. Seasurveys.co.uk

 

[vyv_cox]

You don't say whether the hull is grp or wood. If wood then consider not connecting the anode up to anything as anodes fitted to timber hulls are very destructive to the hull if they are wired to the structure.
John Lilley. Seasurveys.co.ukij

It's a Starlight 39

 

[Tinto]

Yes, there is a folding prop with an anode on the prop shaft. The second image is directly behind the engine and it looks like these cables are connected to an anode.

the first image is where there are two anodes side by side. The one shown is not connected to anything and is leaking water through a through hull bolt.

 

[vyv_cox]

I suggest you dump the lot. The gland is just a joke, clean up and nip the packing up to stop the leaks. The cable going aft may go to the P-bracket?

 

[Tinto]

I suggest you dump the lot. The gland is just a joke, clean up and nip the packing up to stop the leaks. The cable going aft may go to the P-bracket?

the leak from the stuffing box is minor and drains to the bilge where the pump deals with it.

The main leak is aft of that from the anode through hull.

i will double check that cable routing

 

[penfold]

Any electrical connection between the gland housing and the propellor shaft is tenuous at best; if you want an electrically bonded system there needs to be a wiper onto the shaft, there are commercial kits available.

 

[Tinto]

Any electrical connection between the gland housing and the propellor shaft is tenuous at best; if you want an electrically bonded system there needs to be a wiper onto the shaft, there are commercial kits available.

The shaft has its own anode directly fitted to it

 

[johnlilley]

You don't say whether the hull is grp or wood. If wood then consider not connecting the anode up to anything as anodes fitted to timber hulls are very destructive to the hull if they are wired to the structure.
John Lilley. Seasurveys.co.ukij

Next time I'll make every effort to read the post I'm replying to!

 

[Tranona]

Agree. Get rid of all of that. Absolutely no point in having anything connected to the stuffing box housing. It is a great nig lump of bronze and not in contact with any other metal, let alone in seawater. If you have a shaft anode you will probably be able to get rid of both hull anodes. Can see no connection between the hull anode and the shaft therefore it can't be doing anything to protect the prop.

As Vyv says there is a huge amount of misunderstanding about the use of anodes and you need to get back to basics and determine where there are metals together with different potentials in seawater and then devise an anode scheme to deal with them. The 2 you have are the prop and shaft (and possibly the prop itself as I explained above) which are covered with the shaft anode and the prop anode, and possibly the P bracket which is yellow metal fastened with stainless bolts, but if I remember rightly these are inside the boat and painting the p bracket with antifouling is all that is needed.

 

[bignick]

I always understood that the large pear anodes which typically mount onto a double bolt arrangement are there to protect the engine.
if you have a raw water cooled diesel then you have a large surface area of unprotected iron exposed to saltwater, I.e. the internal water pathways. My strategy is to make sure there’s a decent wired connection directly between the engine block and one of the studs.
/Ducks back below the parapet…/

 

[vyv_cox]

I always understood that the large pear anodes which typically mount onto a double bolt arrangement are there to protect the engine.
if you have a raw water cooled diesel then you have a large surface area of unprotected iron exposed to saltwater, I.e. the internal water pathways. My strategy is to make sure there’s a decent wired connection directly between the engine block and one of the studs.
/Ducks back below the parapet…/

Engines cannot be protected by an external anode. The suggestion assumes that an inlet hose full of salt water acts like a piece of wire. Sorry, it just does not happen. You may have read that anodes need to be able to 'see' the item they are protecting. It follows that this is impossible with an engine. Raw water cooled engines usually have an internal pencil anode for their protection.

 

[superheat6k]

I always understood that the large pear anodes which typically mount onto a double bolt arrangement are there to protect the engine.
if you have a raw water cooled diesel then you have a large surface area of unprotected iron exposed to saltwater, I.e. the internal water pathways. My strategy is to make sure there’s a decent wired connection directly between the engine block and one of the studs.
/Ducks back below the parapet…/

That is not correct. Any anode will only protect metals to which its Ions can travel and normally only within a few feet - less in any sort of tidal flow. The somewhat tortuous path back to the engine via the sea water inlet, plus the full blockage created by the circulation pump impeller would completely prevent any ions getting to the coolant system metals.

If you prefer not to disturb the leaky bolt then Captain Tolley's might work. I had a weepy rudder stock bolt on my Turbo 36 that I successfully sealed with numerous drips of CT over a few days (boat ashore) until the crevice around the bolt was completely full.

 

[superheat6k]

Engines cannot be protected by an external anode. The suggestion assumes that an inlet hose full of salt water acts like a piece of wire. Sorry, it just does not happen. You may have read that anodes need to be able to 'see' the item they are protecting. It follows that this is impossible with an engine. Raw water cooled engines usually have an internal pencil anode for their protection.

Or coolers made of a decent corrosion resistant material (this statement does not apply to Volvo Penta in my experience !).

 

[bignick]

Engines cannot be protected by an external anode. The suggestion assumes that an inlet hose full of salt water acts like a piece of wire. Sorry, it just does not happen. You may have read that anodes need to be able to 'see' the item they are protecting. It follows that this is impossible with an engine. Raw water cooled engines usually have an internal pencil anode for their protection.

Many thanks, I’ve learned something new.
i was working on the assumption that electrical continuity would be achieved through the water path.
if they’re not there for that, then what on earth is the pear anode for?

…. And you’re quite correct - my 2GM20 has two tiny, and I do mean tiny, internal anodes.