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Old 29 June 2011, 08:47   #21
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Originally Posted by Erin View Post
The negative post on the battery is not a true 'ground'. To achieve this you would need a proper ground plate fitted to the hull to allow static discharge to the sea. Connecting everything together and linking to the neg post on the battery will not earth the items and may also create corrosion. As Martini stated, his is connected to an anode which will limit corrosion and also act as a partial ground.

Depending on your sender type, the two wires running to it may also not be connected to 12v or 0v but may be just a loop out of the gauge sensing resistance.
Erin, the grounding issue makes sense.

Just one question though. Please don't take this the wrong way, I am just trying to learn as I have recently completed wiring my new 6m rib with a Suzuki DT200 and was hoping I had it right.

I am confused. Assuming that:

(1) The fuel sender (and fuel filler) is connected to the -ve post of the battery;
(2) the engine is connected to the -ve post of the battery;
(3) the engine has an anode as most outboards do.

Will the anode not act as the grounding plate and since it is the least noble metal, will it not limit corrosion elsewhere?
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Old 29 June 2011, 09:46   #22
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Some good guidance here. Pages 20 and 21 in particular:

http://www.boatsafetyscheme.com/down...uide_chap2.pdf
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Old 29 June 2011, 09:49   #23
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Quote:
Originally Posted by Erin View Post
The negative post on the battery is not a true 'ground'. To achieve this you would need a proper ground plate fitted to the hull to allow static discharge to the sea. Connecting everything together and linking to the neg post on the battery will not earth the items and may also create corrosion. As Martini stated, his is connected to an anode which will limit corrosion and also act as a partial ground.

Depending on your sender type, the two wires running to it may also not be connected to 12v or 0v but may be just a loop out of the gauge sensing resistance.
Depending on the engine the -ve battery terminal may give a good ground.
Check the resistance between the -ve battery post and the anode on the transom bracket.
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Old 29 June 2011, 10:24   #24
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Will the anode not act as the grounding plate and since it is the least noble metal, will it not limit corrosion elsewhere?
I agree with you, the only problem is there will be various connections between all of that and there may be too high a resistance to act as a good earth plate. Proper earth plates normally have a large surface area and are of a metal that doesn't corrode and therefore oxidise which might inhibit its effectiveness. Remember also that the anode will only protect other metals against corrosion that are in the same solution causing the corrosion. It won't protect the fuel tank or inboard metal items for example.
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Old 29 June 2011, 11:06   #25
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If you're worried about water damage to the ground wire (if you decide to install one), use a length of stainless steel aircraft cable with crimped eyes at both ends. You're only trying to get electrical conductivity, not carry massive amounts of current.

jky
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Old 29 June 2011, 17:39   #26
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Quote:
Originally Posted by Erin

I agree with you, the only problem is there will be various connections between all of that and there may be too high a resistance to act as a good earth plate. Proper earth plates normally have a large surface area and are of a metal that doesn't corrode and therefore oxidise which might inhibit its effectiveness. Remember also that the anode will only protect other metals against corrosion that are in the same solution causing the corrosion. It won't protect the fuel tank or inboard metal items for example.
Thanks
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