blueglass
Well-Known Member
my engine anodes have been used at an alarming rate - from new down to the bare brackets in 5 months. Normally last a year with loads in hand. what can cause this?
rapid anode wear
- Thread starter blueglass
- Start date
PeterGibbs
Well-Known Member
They are small, and apparently doing the job intended. Rejoice.
But check whether your electrical system (start with the alternator) is routed through the block of the engine, and whether this is correct for your vessel. My recollection is that boat systems are not as in cars where the frame/block is used as a negative return.
PWG
But check whether your electrical system (start with the alternator) is routed through the block of the engine, and whether this is correct for your vessel. My recollection is that boat systems are not as in cars where the frame/block is used as a negative return.
PWG
dickh
Well-Known Member
What engine?
blueglass
Well-Known Member
sorry - twin sabre perkins 225Ti 1997
blueglass
Well-Known Member
[ QUOTE ]
They are small, and apparently doing the job intended. Rejoice.
[/ QUOTE ]
I understand your point but lifting the boat for new anodes every 3 or 4 months is not really an option.
the wiring was always correct before and has not been changed so it should be OK
They are small, and apparently doing the job intended. Rejoice.
[/ QUOTE ]
I understand your point but lifting the boat for new anodes every 3 or 4 months is not really an option.
the wiring was always correct before and has not been changed so it should be OK
VicS
Well-Known Member
[ QUOTE ]
I understand your point but lifting the boat for new anodes every 3 or 4 months is not really an option.
[/ QUOTE ] We are not talking about engine anodes then. ie anodes fitted in the water cooling circuit of the engines.
Are we therefore talking anodes mounted on the hull or an outdrives. Please more description. Also are you in a marina with shore power connected.
Also what items are bonded to the anodes
I understand your point but lifting the boat for new anodes every 3 or 4 months is not really an option.
[/ QUOTE ] We are not talking about engine anodes then. ie anodes fitted in the water cooling circuit of the engines.
Are we therefore talking anodes mounted on the hull or an outdrives. Please more description. Also are you in a marina with shore power connected.
Also what items are bonded to the anodes
blueglass
Well-Known Member
These are anodes(2) fitted to the hull. You can tell I am a numbskull on electrics. As I understand it the anodes are protecting my engine blocks, and sterngear and were checked by an engineer when I bought the boat 4 years ago and were correctly wired up. They have consistently eroded by about 75% in 12 months until this recent rapid increase, following a move to the Med. During the relevant 5 months the boat was intermittently at anchor and in many different marinas (we have no fixed base) and is currently overwintering on the hard. I would say about half of that period of 5 months would have been in a marina with shorepower connected.
Rowana
Two steps lower than the ships' cat
[ QUOTE ]
These are anodes(2) fitted to the hull. You can tell I am a numbskull on electrics. As I understand it the anodes are protecting my engine blocks, and sterngear and were checked by an engineer when I bought the boat 4 years ago and were correctly wired up. They have consistently eroded by about 75% in 12 months until this recent rapid increase, following a move to the Med. During the relevant 5 months the boat was intermittently at anchor and in many different marinas (we have no fixed base) and is currently overwintering on the hard. I would say about half of that period of 5 months would have been in a marina with shorepower connected.
[/ QUOTE ]
I think this is your answer - Med=warmer water=more erosion.
Time spent in marina with shore power connected=High possibility of more erosion.
Personally, I think you have nothing to worry about as the anodes are doing their job.
You do have a galvanic isolator on the shore power, don't you? If not, get one fitted ASAP.
These are anodes(2) fitted to the hull. You can tell I am a numbskull on electrics. As I understand it the anodes are protecting my engine blocks, and sterngear and were checked by an engineer when I bought the boat 4 years ago and were correctly wired up. They have consistently eroded by about 75% in 12 months until this recent rapid increase, following a move to the Med. During the relevant 5 months the boat was intermittently at anchor and in many different marinas (we have no fixed base) and is currently overwintering on the hard. I would say about half of that period of 5 months would have been in a marina with shorepower connected.
[/ QUOTE ]
I think this is your answer - Med=warmer water=more erosion.
Time spent in marina with shore power connected=High possibility of more erosion.
Personally, I think you have nothing to worry about as the anodes are doing their job.
You do have a galvanic isolator on the shore power, don't you? If not, get one fitted ASAP.
VicS
Well-Known Member
OK then.
Anodes must be fitted fairly close to and "within line of site" of the items they are to protect and be bonded to them with a good low resistance electrical connection. (Line of sight does not have to be taken too literally, they can see round curves!)
That means hull anodes do not in any way protect your engines' cooling systems. If they are raw water cooled they probably have their own internal anodes which will require regular replacement (See the engine manual) if they are fresh water cooled the heat exchangers may have anodes in the salt water side.
To give protection to stern gear the only 100% sure way of providing a good electrical connection is with brushes running on the shafts inboard of the stern glands. The alternative is of course shaft anodes.
Bronze (or DZR brass) skin fittings should not normally require protection but if they do they should not be connected to the same anodes as other ferrous bits and pieces. Even a bronze prop on a stainless shaft probably does not need protection but it is often provided as a precautionary measure (or to swell the anode makers profits)
If your problem has only arisen since moving to your current marina and you normally leave the shore-power connected then stray currents conducted via the shore power connection are the most likely cause of your problems. You should therefore fit a Galvanic isolator in the shorepower earth connection. Or check that an existing one is correctly fitted and functioning correctly.
MGDuffs website will be worth a read.
Also for explanation of a GI http://www.yandina.com/galvanicIsolator.htm
Re-read your last post and realise you have been in sevearal marinas, nevertheless the comments about the GI still apply.
Anodes must be fitted fairly close to and "within line of site" of the items they are to protect and be bonded to them with a good low resistance electrical connection. (Line of sight does not have to be taken too literally, they can see round curves!)
That means hull anodes do not in any way protect your engines' cooling systems. If they are raw water cooled they probably have their own internal anodes which will require regular replacement (See the engine manual) if they are fresh water cooled the heat exchangers may have anodes in the salt water side.
To give protection to stern gear the only 100% sure way of providing a good electrical connection is with brushes running on the shafts inboard of the stern glands. The alternative is of course shaft anodes.
Bronze (or DZR brass) skin fittings should not normally require protection but if they do they should not be connected to the same anodes as other ferrous bits and pieces. Even a bronze prop on a stainless shaft probably does not need protection but it is often provided as a precautionary measure (or to swell the anode makers profits)
If your problem has only arisen since moving to your current marina and you normally leave the shore-power connected then stray currents conducted via the shore power connection are the most likely cause of your problems. You should therefore fit a Galvanic isolator in the shorepower earth connection. Or check that an existing one is correctly fitted and functioning correctly.
MGDuffs website will be worth a read.
Also for explanation of a GI http://www.yandina.com/galvanicIsolator.htm
Re-read your last post and realise you have been in sevearal marinas, nevertheless the comments about the GI still apply.
blueglass
Well-Known Member
useful info here - many thanks - will look into the galvanic isolator thing - not sure at all if I have one fitted - will check at next visit.
as regards the warmer med water - I did think of this but chatting to other med boat owners they were not having the same problem. It is possible of course that one or more of the marinas visited had shorepower probems.
as regards the warmer med water - I did think of this but chatting to other med boat owners they were not having the same problem. It is possible of course that one or more of the marinas visited had shorepower probems.
pappaecho
Well-Known Member
Basic rule of physical chemistry. Q10=2, which means that if you raise the temperature by 10 degrees C, the rate of reaction doubles.
So if you look at the average sea temperature in your location in the UK, and your new location in the Med, then I wager it is close to 10 degrees C different.
Move to the Antartic, but avoid hitting Ice Cubes, and the anode will last 10 years
So if you look at the average sea temperature in your location in the UK, and your new location in the Med, then I wager it is close to 10 degrees C different.
Move to the Antartic, but avoid hitting Ice Cubes, and the anode will last 10 years
damo
Well-Known Member
And in the Antarctic there will be less likelihood of marina-induced corrosion /forums/images/graemlins/smile.gif
blueglass
Well-Known Member
yes I understand the basic premise of faster reactions in higher temperatures but other boats in the same temp water are not so afflicted. When I say mine were down to the brackets I mean just that - no anode material whatsoever remained, after 5 months. Therefore to allow safety margin, (usual recommendation is to replace when over 50% eroded) I need to replace every 3 months - can't be right. I guarantee all the med boats are not being lifted for new anodes every 12 weeks.
vyv_cox
Well-Known Member
I agree. I don't see any faster anode loss in Greece than I did in UK or in Holland. Somehow your anodes are being subjected to a voltage, either AC in marinas or DC sourced somewhere on your boat.
DiamondHead
Member
switch off your battery charger and check if your battery is being discharged rapidly.
Piers
Well-Known Member
Bigger anodes?
William_H
Well-Known Member
I would suggest that the problem might be caused by the shore power. Disconnect for a period from the shore power ie pull the plug not just switch off and observe anode wastage.
The problem is often that the shore power earth is finding its way to your ships earth negative battery etc and that current is eating the anodes.
Now at the risk of repeating myself from recent posts...
The shore power in a simple system does not have to be connected to the ships earth in any way. However a battery charger may connect the mains earth to the battery earth causing problems.
On a sophisticated 240V installation the mains earth is connected to the ships earth for safety from possible electric shock. Now rather than just wire the 2 together a galvanic isolator is used. It is a stack of diodes set up so that it takes a voltage above 1.5 volts before any current can flow. As corrosion currents are usually quite a tiny voltage they are stopped but any real fault earth current can run through.
Now a GI is of no use if it is bypassed inadvertantly by some other connection ships earth to the mains earth via metal appliance body or the battery charger. So after disconnecting the mains plug you could check with a multimeter to see if there is any conduction between the mains earth pin and the ships nagative.If there is you need to find it. Or stop using mains power 24/7. Occasional use shouldn't hurt. olewill
The problem is often that the shore power earth is finding its way to your ships earth negative battery etc and that current is eating the anodes.
Now at the risk of repeating myself from recent posts...
The shore power in a simple system does not have to be connected to the ships earth in any way. However a battery charger may connect the mains earth to the battery earth causing problems.
On a sophisticated 240V installation the mains earth is connected to the ships earth for safety from possible electric shock. Now rather than just wire the 2 together a galvanic isolator is used. It is a stack of diodes set up so that it takes a voltage above 1.5 volts before any current can flow. As corrosion currents are usually quite a tiny voltage they are stopped but any real fault earth current can run through.
Now a GI is of no use if it is bypassed inadvertantly by some other connection ships earth to the mains earth via metal appliance body or the battery charger. So after disconnecting the mains plug you could check with a multimeter to see if there is any conduction between the mains earth pin and the ships nagative.If there is you need to find it. Or stop using mains power 24/7. Occasional use shouldn't hurt. olewill
blueglass
Well-Known Member
I know this doesn't occur as I leave the boat unconnected to shorepower when I am at home and come back weeks later and batteries have always retained good charge - what does that tell you (me)
blueglass
Well-Known Member
thanks olewill - I'll make it a habit not to leave power permanently connected and look into GI installation.
Thanks others also for useful advice - well received.
Thanks others also for useful advice - well received.
