Mercathode question, is this normal?

[makonnen]

So I don't normally work on my outdrive when its raining. But I did today and I keep getting shocked.

Here is the scenario:

- the boat is plugged into shore power
- when I touch the outdrive with my bare hand, and touch the wet cemet ground (ie: very wet), I get shocked.
- when I touch the outdrive with my bare hand, and do not touch the wet cement ... I'm OK (wearing insulated work boots)
- when I'm working INSIDE the boat, touching the engine, risers etc... I don't get shocked.

Is this normal? Do I have a 110V shore power problem or is it jut the Mercathode working?

 

[Don S]

Re: Mercathode question, is this normal?

If you touch anything on your boat and get shocked, you have a BIG problem. Unplug the shore power until you find the problem, or you may destroy your drive and anyone elses around you.
If your shore power is unplugged, do you still get shocked?? This is not a Mercathode problem.

First contact the marina and explain the problem to them

 

[Failproof]

Re: Mercathode question, is this normal?

Is this boat trailered currently, in your drive? You know, pluged into YOUR house? Could have ground issues with power supply, shore power cord, or nuetral/ground inside the craft.

 

[makonnen]

Re: Mercathode question, is this normal?

Its on a trailer ... and it was plugged in...

pls excuse my dumb quetions ... but I'm not very good at 110V AC electrical.

Its plugged into the house, but the extension cord to the house outlet has the third / ground connector broken off on one side. Could this be the cause?

I'm going out with a different extension cord and a DVM to check this out.

Thanks for the quick responses!

 

[tpenfield]

Re: Mercathode question, is this normal?

Its on a trailer ... and it was plugged in...

pls excuse my dumb quetions ... but I'm not very good at 110V AC electrical.

Its plugged into the house, but the extension cord to the house outlet has the third / ground connector broken off on one side. Could this be the cause?

I'm going out with a different extension cord and a DVM to check this out.

Thanks for the quick responses!

sounds like you have 110 running around the boat. Obviously, not a GFI outlet that you are plugged into. Don't learn about 110volts the hard way

 

[makonnen]

Re: Mercathode question, is this normal?

Well, it was a broken ground terminal on the extension cord...

One more time guys, is THIS normal now?

- Its pouring rain right now, ground is soaked ...
- I put a DVM between the leg and the wet concrete - reading 110VAC
- I unplugged the extension cable with the broken ground terminal - reading ~2VAC (fluctuates)
- I replaced the extension cord with one that has good ground terminals - reading ~0.4VAC (fluctuates)

 

[glenn property of pam]

Re: Mercathode question, is this normal?

simple electrical. when connected to shore power the boat should be grounded by the ext cord. (some boats the netrual and ground are connected by the generator or panel) buy a cheap plug tester and it will show you if it is correctly connected and wired. if the ground is good then the boat should never be 110v to wet concrete unless the plug is wired incorrectly and the netrual, live and ground have been swapped (seen this happen on ext cords). the only other possible ans would be that the boat is ground and you have a problem somewhere else like a cut in the ext cord thats tracking by the water trying to find a ground and you become the path of least resistance when you touch the boat.

 

[makonnen]

Re: Mercathode question, is this normal?

Well I guess in this case, the ground prong of the extension cord was missing on one end. That would explain the 110V between the leg and the wet pavement. When I replaced the extension cord with one that hasa good ground prong ... that got rid of the 110VAC between the leg and the wet pavement.

Explain to me like the idiot that I am (with AC) ... what is the difference between Live, Neutral and Ground? From what little I know about 110VAC, there are two live wires where the current alternates back and forth and there is a ground prong. I always thought the ground prong is optional ... its there for safety only. That is, the ground prong provides the the shortest path to ground in case the device has a short to the case.

 

[glenn property of pam]

Re: Mercathode question, is this normal?

think of ac as one wire power. the power station pushs and pulls on the same wire at 60 times a second. the netrual does not push or pull but is pushed and pulled and is connected to earth ground. the power company is the largest earth grounding device in the country as its connected to every house and under a power station the grounding grid is huge. the reason they use the earth as a ground is for safety so when you drive your car into a power pole and it falls over it can give the electricity a path that will trip the breakers. the netrual is connected via cables back to the power station and as the netrual is lower resistance than the earth (soil) power will flow on the netural when there isnt a problem. the ground in the house is never meant to carry any power its a emergency path back to the power station the same as in the house. people get confussed because netrual is tied to ground at there incoming power pole. the netrual is classed as a power wire and if you make the mistake of cutting a netrual and thinking its a ground you will end up getting zapped off the side that is no longer connect to the power station (live went to a light then back via the netrual then you cut it and touched it now it went to the light then you to ground and you get poked). so now the question is why doesnt every thing in the house have a grounded plug (well thats called double isolation or in simple terms its made out of plastic so theres no need for a emergency path as no part of it can carry power in normal use. all metal tools etc will have the grounded plug and anything in a kitchen near water or used outside will be plugged into a gfci). ac is dirty and it can create a field in the metal of a item like a boat so when connected to shore power the boat can have a potential even when there is no electrical problem on the boat and when you touch the boat you equalise the potential to ground and get shocked. if there is a electrical problem like a live wire has touched a metal part and there is no path to ground especially on a trailer and you touch the boat then you become the light bulb between the boat and the ground and if 50ma (0.050 amps) crosses your heart then you can die. a 20 amp breaker trips at 20000 amps thats a little more than the 0.050 required good thing is we dont conduct electricity(110v) to easy unless we are wet so please dont test a boat by touching it with one hand and touching wet concreate with the other hand as the electicty will go hand to hand and the heart is in that path somewhere and it can kill you. this have been simplified to help people who dont work in the electical field.