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Old 29 March 2012, 22:20   #11
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Ok all joking aside now, any chance of some ideas on what the problem might be and what to check on. Bad earth seems likely but what to look at ?
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Old 29 March 2012, 22:58   #12
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Like I said 10 posts ago. Trouble is it could be anywhere. I had a same problem on a boat and found they had used one single wires on the nav lights and earth the a frame. When everything got damp you are the better earth.
Could be anywhere. Start in the controller
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Old 30 March 2012, 07:04   #13
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To get a shock the voltage would have to be quite high therefore not the normal electrics (12/24V).

It could be static or something on the high voltage side of the engine.

The running on (assuming it's a keyed ignition) would indicate that there is still some flow of current. This could be induced from another circuit.

Some things you might try are:

do the problems occur if only the engine has been started without the boat being driven,
after driving do you get more than one shock by doing the same thing,
is it related to any particular instruments.
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Old 30 March 2012, 08:13   #14
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Quote:
Originally Posted by EnglishLes View Post
To get a shock the voltage would have to be quite high therefore not the normal electrics (12/24V).
For what it's worth I agree with Biffer on this one - it doesn't have to be more than 12 volts!
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Old 30 March 2012, 13:24   #15
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If you're wet, 12v gives quite a tingle.
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Old 30 March 2012, 13:41   #16
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It is the current flow that gives the shock/tingle, not the voltage. The PD (that's potential difference not PikeyDave) required to give said shock depends on the resistance of the path to earth. Obviously if you are wet and holding on to a 'live' A-frame with one hand whilst the other is in the briny then your resistance to earth is going to be much lower than if you were dry and not touching the sea. Normally you require a high voltage to get a shock as the resistance is too high for a meaningful current to flow. Bear in mind 9v is enough to give a tingle as anyone who has tested a PP3 battery on their tongue will attest . Over 30mA is deemed dangerous hence why household RCD's usually trip at 30mA. The old party trick of static electricity in a balloon which makes your hair stand up is many thousands of volts, but there is insufficient 'charge' and therefore current available to electrocute you (otherwise there'd be a lot of demised kids entertainers and children!).

Also, if there is any coil or transformer that is causing the stray current then the shock is greater if it is switching. The induced reverse voltage as a coil is switched off is very high, hence why coils are used for ignition. It could be an ignition fault due to moisture in the engine or a damaged HT lead giving this stray current.
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Old 30 March 2012, 15:36   #17
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On that engine check that the earth strap from the powerhead to the lower cowl is ok if not it will earth through you. Look at item 27 on the parts diagram it should be around that area.
Attached Files
File Type: pdf 60earth.pdf (143.9 KB, 58 views)
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Old 30 March 2012, 17:31   #18
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Thanks everyone, will be looking at it tomorrow now
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Old 30 March 2012, 17:46   #19
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Quote:
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Obviously if you are wet and holding on to a 'live' A-frame with one hand whilst the other is in the briny then your resistance to earth is going to be much lower than if you were dry and not touching the sea.
And there it is: Resistance. If you're wet and salty, you can get a tingle off almost anything (reminds me of my old college days )
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Old 30 March 2012, 17:47   #20
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Bear in mind 9v is enough to give a tingle as anyone who has tested a PP3 battery on their tongue will attest
You were at the wrong parties
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