1GM10 earth/insulated return

mitiempo said:
If you move to a marina and have corrosion issues and zincs not lasting long, it is either the marina's wiring or the ac on another boat. Not the dc on yours. Through hulls in my opinion should not be bonded.
Nigel Calder must have changed his mind because that certainly is not in my copy.
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It is likely the fault would be as you suggest with the marina's wiring or the ac on another boat (although there are other possibities), but this is little consolation if your boat is the one that is corroding. Connecting your battery negative to the water in the marina does increase the chance of corrosion in these circumstances.
I am not sure about Nigal Calders current view, but I have seen the recomdation of isolating the engine in several articles. If I was rewiring a fiberglass boatfor the small amount of extra cost and trouble I would isolate the engine.
 
There is no actual fault right now(galvanic or otherwise with the exception of the master switch), it's just the general state of the wiring that needs attention and I am taking the opportunity to generally upgrade.

But thank you for all the input!
 
Bog standard Hitaichi alternator would not be an easy job to double insulate, to forget the starter and leave earth return, still has to be supplied on the negative to the battery. I have never seen a starter that fits your engine that is fully insulated, but thats not to say there isnt, if there is, I`v been in the wrong industry for years. IMHO the insulated system whist being the ultimate, for this engine is a complete waste of time also taking as gospel all that you read can take you down the wrong route.

Other posters have pointed out the main reasons for not going down the the route suggested.But I wish you well in your quest for perfection ,
 
pampas said:
Bog standard Hitaichi alternator would not be an easy job to double insulate, to forget the starter and leave earth return, still has to be supplied on the negative to the battery. I have never seen a starter that fits your engine that is fully insulated, but thats not to say there isnt, if there is, I`v been in the wrong industry for years. IMHO the insulated system whist being the ultimate, for this engine is a complete waste of time also taking as gospel all that you read can take you down the wrong route.

Other posters have pointed out the main reasons for not going down the the route suggested.But I wish you well in your quest for perfection ,
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I understand that the alternator isn't insulated and should be for that perfection that you talk so fondly of, but surely a heavy copper cable from the alternator case to a "common ground point" would provide an easy path for earth leakage and therefore remove that same earth leakage from the engine block???

Thanks again!
 
pampas said:
Bog standard Hitaichi alternator would not be an easy job to double insulate, to forget the starter and leave earth return, still has to be supplied on the negative to the battery. I have never seen a starter that fits your engine that is fully insulated, but thats not to say there isnt, if there is, I`v been in the wrong industry for years. IMHO the insulated system whist being the ultimate, for this engine is a complete waste of time also taking as gospel all that you read can take you down the wrong route.

Other posters have pointed out the main reasons for not going down the the route suggested.But I wish you well in your quest for perfection ,
Click to expand...

The current Hitaichi 80A alterternator used by Yanmar is already isolated, but I am not sure about the 60A or older models. An isolated starter is not used by most metal boats because a simple cheap relay achieves the same thing apart from the few seconds starting the engine.
 
On any boat with an AC system there has to be an earthing connection for safety reasons and that is logically the engine block. This would apply to most boats. I know of no other way to safely do it. And you say you have no corrosion issues. If it isn't broken why try to fix it?
 
co256 said:
I understand that the alternator isn't insulated and should be for that perfection that you talk so fondly of, but surely a heavy copper cable from the alternator case to a "common ground point" would provide an easy path for earth leakage and therefore remove that same earth leakage from the engine block???

Thanks again!
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The earth leakage that is of concern is from the battery negative. The idea is to break the curcit and isolate the - from the engine block. Unfortunately grounding the engine at one point will not acchieve the same thing.
 
Hello again!

Well this has moved on in the two hours I'v been away from the computer!

But what a mish mash and a muddle!

Firstly if you have no problem them you really do not need to go to extreme lengths to cure it however I appreciate that your boat needs rewiring and you want to do it properly.

I dont think you have said what sort of boat you have, wood, grp, steel, or aluminium. If you have steel boat there may be some case for an isolated negative return a stronger case if you have an aluminium hull or a sailddrive but with a GRP or wooden boat I think there is little or nothing to be gained.

I don't have Calders book and I am not prepared to discuss any extracts from it out of context, except to say that I am not sure of his logic behind,
" A good compromise is to connect a heavy ground cable from the alternator case to the boat's common ground point. This will provide a direct electrical path to the battery that bypasses the engine block, discouraging leakage currents."​

However you can do what you are asking about.

Firstly you either need an alternator with an insulated negative or you take Calders statement at face value. However, if you do as Cader suggests you then have the engine block connected to the battery negative etc means any galvanic corrosion that might have occurred as a result of the non-insulated negative will still occur. The bonding that Cader suggests will stop electrolysis that might occur at bad connections wet with seawater.

At this point a short digression to point out that electrolysis is what occurs when a current is passed (forced) from a power source between two "electrodes" (which may be the same material) immersed in an electrolyte (seawater) but galvanic corrosion is what happens as the result of two "dissimilar metals", which are connected to each other, being immersed in the electrolyte. Similar results maybe but the importance is the subtle difference in the cause. Current from a power source on the one hand, current from a pair of dissimilar metals on the other ​


Next you need the "two wire" type of sensors for oil pressure an water temperature

Then you need to consider the starter motor. No idea if insulated return starters are available to fit your engine, probably not! However this problem is easily overcome as Noelex has already indicated by utilising an earthing relay. This is a heavy relay, capable of carrying starter motor currents, that is energised from the key switch, while in the preheating and starting positions, to connect the engine block to the battery negative thereby providing the return path for the glowplug current and starter current, This is a system that you will find used on some of the Volvo Penta engines (2010 etc IIRC ) when used with a sail-drive.

Beware of statement like "The seawater cooing provides a possible path for conduction and therfore corrosion of other metal structures such as the rudder stock." Made by Noelex. It is a red herring as far as connection between metal bits and pieces is concerned in the case of galvanic corrosion. The relevant connection is a connection with a metal conductor or direct contact .
One metal, seawater, another metal more seawater back to the first metal does not make a circuit for galvanic corrosion to occur.

Corrosion due to connection to a shorepower source has been dragged into the discussion. It is a different issue altogether. If you are not in a marina with a permanent shorepower connection it is irrelevant and is bridge that can be crossed as and when the need arises.

Apologies to contributors whose posts this crosses, its been more than a few minutes in being compiled.
 
mitiempo said:
On any boat with an AC system there has to be an earthing connection for safety reasons and that is logically the engine block. This would apply to most boats. I know of no other way to safely do it. And you say you have no corrosion issues. If it isn't broken why try to fix it?
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My "generator" is 12v and I rarely connect to AC but there are two ways to attach the AC system. The way you describe above above and a disconected earth system with a low value safety switch. Nigal Calder wrote a long article in Proffesional Boat Builder a few years back. It discussed the pros and cons of both systems.
 
Thank you vicS

Your digression helped!

It has to be re-wired whatever so I figure I may as well follow the best advice I can get.

As it is the main battery switch doesn't disconnect the power in either the on or off positions..... reason enough to re-wire!!!!!

I think that concludes this thread and thank you all once again.

Out.
 
two ways to attach the AC system. The way you describe above above and a disconected earth system with a low value safety switch. Nigal Calder wrote a long article in Proffesional Boat Builder a few years back. It discussed the pros and cons of both systems.
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Relevant to that comment but not to the original question. the current version of ISO 13297 allows the shorepower earth not to be connected to the DC negative provided there a "whole craft" RCD is fitted. The American reqirements differ IIRC low current RCDs (10mA?) are required in heads cubicles etc. It may well be that low current RCDs will be needed in the incoming supply to protect swimmers in the vicinity but I suspect they will result in a lot of nuisance trips .

IIRC the link to Calders article in ProBoat magazine was first posted by Mitiempo. It is http://www.proboat-digital.com/proboat/200604#pg58
 
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