electric current / prop strut

[NYSail]

Hello all,I was changing my cutlass bearing on my P36-2 last weekend and charging my batteries at the same time....plugged it. When I touched the strut, I felt a slight electrical current. When I unplugged, the current went away.I guess this is a bad ground? I did not check my bolts for the strut as they are under an aluminum exhaust mixer and not easily accessable. I am in no way an electrical expert so pardon my ignorance when it comes to this.What might be causing this (I know electric current, but what is wrongly hooked up), is this atypical, and what should I do??Thanks in advancedGreg

 

[Ross]

What did you unplug? You shouldn't be

able to feel the effects of 12 volts. Probably you have a ground fault in the 120 volt AC wiring. Have an electrician check it out! Had you been bare foot and standing in a puddle you might not have been able to post this problem.

 

[Phil]

This needs some review

I can't think of any reason this woould be a good thing. If you AC is what was unplugged and you no longer felt it, not good. I am thinking stray AC and water don't mix real well.

 

[Bill Roosa]

You can feel 12 volts

give the right situation you can feel 12 volts quite easily. A 9 volt battery to the tounge should prove that.To diagnose something like this we'll need some specifics; built in battery charger or a stand alone one? shore power or are you using a ground mounted genset?My gut tells me that you have a bad AC shore power ground and a battery charger that is bleeding off current to the ground circut but that would be a big fat guess.

 

[Mike F.]

Sticky shift cable

For a few years now, I have noticed a notchyness (is that a word?) in my shift cable. It would be great if I could smooth this out, but, I hate to replace the cable, only because it would be a pain to re-adjust the linkage to the fwd-n-rev rod. I did it when I bought the boat and it was tedious.Can these cables be lubricated? Does anyone do this?

 

[Ross]

Bill, I guess that my skin resistance is

too high. With dry hands I can detect 120AC with a light touch, no I don't wire things hot but sometimes I find two circuits in one box. I never have felt 12 volts. 24 volts doorbell circiuts I can't feel if I pinch the leads between my thumb and finger.But, on subject I'm betting on an AC ground fault.

 

[Mike F.]

Sorry for mis-placing question

Sorry, I stuck in a question of mine unrelated to your question. (the sticky cable)However, I experienced something similar to what you did. I was in drydock using shore-power. Ran it through my AC system to all outlets on board. I failed to notice that I had a two prong adapter in the extension cord leading to the boat. I got a slight tingle when I touched the wheel. YIKES! I decided I was not grounded properly. Since I discovered the "two-prong" and removed it I have not seen this problem again.

 

[Phil]

Not trying hard enough

RossIf you start running enough amps thru the line you'll feel it. Just because its 12volts doesn't mean it can't knock you on you butt or even take you out. Grab a hold of the + & - of a 2x 8D bank and I bet it will get your attention. DON'T DO THAT REALLY (Darwin award material)Doorbells and batteries are stepped down and very low amp to protect people.

 

[Ross]

Phil, I can't help you if you believe

that available amps is the determining factor in feeling an electrical shock. You need the voltage to drive the current. The size of the battery bank has nothing to do with the output voltage. When I was a boy we had a 32 volt system on the farm. It consisted of glass cells about 8 inches square and about 18 inches tall each supplying 2.1 volts. These were connected in series to provide 32 volts. We had a gasoline powered generator set to charge the batteries. The electric grid didn't yet reach our farm. Each cell had its own built-in hydrometer that consisted of red, white and green balls in an internal guide. each of these cells was about 250 ampere hour rated, yet you could lay you hand on them harmlessly but if you dropped a wrench on them there was hell to pay.When I was in the Physics Lab we kept stranges from messing with things by labeling them "Danger 10,000,000 OHMS". They walked a wide circle around these things.Voltage is the force that pushes electrons that flow as current and is measured as amperes. When the current flow through your body exceeds 5 miliamps you can feel it, when it exceeds 15 miliamps it can kill you. If you can make connections to your body with very low resistance then a reletively low voltage can push enough current to kill you.

 

[NYSail]

Two Prong

After reading these responses I went to my boat and noticed the extention cord I am using has the ground prong pulled out, so I only have the two main prongs......Maybe this is the problem??Greg

 

[Ross]

Nysail, I think you got it

There is still some stray current involved that needs to be corrected.

 

[Gord May]

<issing AC Gnd.

Yes, the missing AC Ground is your problem. Rectify this immediately.

 

[NYSail]

Done

And no current flowing into my hands when I touch the strut. Funny, my wife never felt the electrical charge in the strut. I guess I am the sensitive one in the family.........As always, thanks for all the help and advise!!!Greg

 

[Ross]

Nysail, do you have a digital

multimeter? if so have your wife, kids, friends and yourself measure your dry skin resistance. It can vary all over the place. just set the meter on resistance and grasp a probe in each hand and read the result. It won't hurt. Also set it on the lowest volt range am hold the probes and watch the readings fluctuate as you flex your muscles.

 

[Franklin]

Now here is the tough question

Why is it that when the ground wire connection is broken, the electricity can travel throughout the boat?

 

[Ross]

For this you have to understand

the nature of electrical wiring. The neutral wire in an AC system is sometimes taken to ground in some tools and sppliances. This is why all plugs are polarized now. That is, one prong is wider than the other. If there is a break in the insulation in a heater, motor, transformer or even a switch, some of the current can leak to the metal parts of the boat. For this reason they make groung fault circuit interrupters. If for any reason the current flow in the power supply isn't the same in both wires the GFCI will trip.

 

[Bill Roosa]

Ross

Guess you and I are just too dried out to have 120 volt AC bother us much anymore.The places that I have felt 12 volts is when I'm soaking wet (rain) and I'm standing in a pool of water (ground) and there is another person (of similar damp construction) who is also working on the electrical system. AlsoFor the record ABYC recomends all AC appliances have a 3 prong connector or be wired for hot-neutral-ground. This is a true pain in the rear when you are looking for AC lamps as ALL the ones that I have found only have 2 prong plugs. Same, Same for power tools

 

[Ross]

Most power tools are double insulated.

That is why the two prong plugs.

 

[Gord May]

sensitivity

My brother (also an electrician) is much more electrically (but not socially) sensitive than I. He can detect a voltage less than half of that which I notice. All receptacles (wall plugs) shall be grounding (three wire) type, but there’s no problem plugging a double insulated two prong device into a three prong grounding outlet.