DC shocks on boat

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chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
I was out with a buddy on his boat yesterday and he was getting shocks from the metal steering wheel. Says this has been going on for a while. I would touch it myself and never felt anything. It was a little rough yesterday and the console and battery compartment had a fair amount of salt water on them.

Any ideas what could be causing this and how to correct it?

Thanks.
 

cadpoint

Senior Member
Location
Durham, NC
The battery should be encased or at least protected from direct or even indirect weather exposure and most be raised off the floor of the boat!

I'll assume fiberglass, boston whaler open body type boat.

If they remove the boat daily from the water you'll never find the short. Depending on the type of motor might also be a determing factor of how long the hunt is.

Inboard/outboard wil be the worst hunt. Check all the wiring and the chassie bound
at the motor and the motor wiring also.

It'll be at the rub point, or transistion point of the wire harness, note the type of wire that they do use, I'd only replace any run with 105C wire more for the jacket protection, think appliance wire.

HAPPY BOATING...
 

Electric-Light

Senior Member
I was out with a buddy on his boat yesterday and he was getting shocks from the metal steering wheel. Says this has been going on for a while. I would touch it myself and never felt anything. It was a little rough yesterday and the console and battery compartment had a fair amount of salt water on them.

Any ideas what could be causing this and how to correct it?

Thanks.

I don't see how this can happen if the frame and steering wheel are at equal potential.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
110530-0824 EDT

Chris:

Years ago when car batteries were 6 V and the horn ring was hot with 6 V relative to the car body I noticed a tingle when I touched the horn ring and my arm was in contact with the door. Things weren't all plastic then. This was a hot humid day and i was sweating.

Its not the voltage, but rather current that produces the tingle. So 1 V and maybe less will give you a tingle. Your skin surface resistance at low voltages will have a big impact on this current. My normal surface resistance is 500,000 to 1 megohm, but hot and sweaty a lot less. There are some people with a normal resistance of maybe less than 50,000 ohms. 50,000 ohms at 12 V is 0.24 milliamperes. Out in salt water conditions there could be surface leakage in the boat and wet hands, and thus total series resistance conditions low enough to get enough current to feel a tingle.

.
 

cadpoint

Senior Member
Location
Durham, NC
I now work wiith a former auto mechanic, I hit him with trivia car questions about my auto and other subjects as they come up. One discussion was about about battery terminials conductors how the ends might corriode, he reminded me that the corrision might migrate way into the wire and one will never know. with pin hole leakage from age or enviroment this alone might be the source.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
I now work wiith a former auto mechanic, I hit him with trivia car questions about my auto and other subjects as they come up. One discussion was about about battery terminials conductors how the ends might corriode, he reminded me that the corrision might migrate way into the wire and one will never know. with pin hole leakage from age or enviroment this alone might be the source.

I owned an automotive electrical repair facility for over a decade. I never saw the large conductors going to the battery with migrated corrosion, but I saw many cases where water wicked up inside the insulation of smaller copper conductors. The result was a black patina that wasn't bad at conducting electricity, but made the wires impossible to solder properly.
 

hurk27

Senior Member
110530-0824 EDT

Chris:

Years ago when car batteries were 6 V and the horn ring was hot with 6 V relative to the car body I noticed a tingle when I touched the horn ring and my arm was in contact with the door. Things weren't all plastic then. This was a hot humid day and i was sweating.

Its not the voltage, but rather current that produces the tingle. So 1 V and maybe less will give you a tingle. Your skin surface resistance at low voltages will have a big impact on this current. My normal surface resistance is 500,000 to 1 megohm, but hot and sweaty a lot less. There are some people with a normal resistance of maybe less than 50,000 ohms. 50,000 ohms at 12 V is 0.24 milliamperes. Out in salt water conditions there could be surface leakage in the boat and wet hands, and thus total series resistance conditions low enough to get enough current to feel a tingle.

.

I was working on an old car of my dads once, and was replacing the horn, it was a coil contact type that would pull in and break the supply contact and this would cause the oscillation creating the sound as the armature was connected to a diaphragm, it also would create an AC ripple and inductive kick back, as high as 200 volts, while I was holding onto the wire feeding it, and my dad was pushing the horn button on the dash it knocked me for a loop, it wasn't till a few years later when I learned about spark gap oscillators and inductive kick back did I understand how I could get such a shock from a 6 volt system.
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
The battery should be encased or at least protected from direct or even indirect weather exposure and most be raised off the floor of the boat!

I'll assume fiberglass, boston whaler open body type boat.

If they remove the boat daily from the water you'll never find the short. Depending on the type of motor might also be a determing factor of how long the hunt is.

Inboard/outboard wil be the worst hunt. Check all the wiring and the chassie bound
at the motor and the motor wiring also.

It'll be at the rub point, or transistion point of the wire harness, note the type of wire that they do use, I'd only replace any run with 105C wire more for the jacket protection, think appliance wire.

HAPPY BOATING...

I took a look at the battery compartment and although this is an older vessel, my buddy did a jamb up job and spared no expense in this aspect. Your right about the type of boat.(glass) Motor is a 1.6L outboard.

I don't see how this can happen if the frame and steering wheel are at equal potential.

As noted above the frame is glass, but we were standing barefoot in salt water and the battery compartment had been infiltrated by salt water also.

110530-0824 EDT

Chris:

My normal surface resistance is 500,000 to 1 megohm, but hot and sweaty a lot less. There are some people with a normal resistance of maybe less than 50,000 ohms. 50,000 ohms at 12 V is 0.24 milliamperes.

I can picture the conversation at your house;

Gordan's wife yelling into mancave:

"Trash needs to go out!"

Gordan:

"In a minute honey, I'm measuring my skin resistance."

And the most interesting member at MH award goes to..

Out in salt water conditions there could be surface leakage in the boat and wet hands, and thus total series resistance conditions low enough to get enough current to feel a tingle.

.
And my callused hands and feet and different physiology prevented me from conducting enough current to feel it? So after my inspection of the system revealing no glaring problems, under the conditions described these events could be described as normal?
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
I was working on an old car of my dads once, and was replacing the horn, it was a coil contact type that would pull in and break the supply contact and this would cause the oscillation creating the sound as the armature was connected to a diaphragm, it also would create an AC ripple and inductive kick back, as high as 200 volts, while I was holding onto the wire feeding it, and my dad was pushing the horn button on the dash it knocked me for a loop, it wasn't till a few years later when I learned about spark gap oscillators and inductive kick back did I understand how I could get such a shock from a 6 volt system.

Was that as much fun as being knocked for a loop by a plug wire?
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
110530-1608 EDT

hurk:

I am sure you would get a big jolt from the several hundred volts produced from the horn oscillating.

But to make it clear to everyone the horn ring was the switch between the horn and ground, maybe there was a relay between the horn ring and the horn, these days there is a relay. So when not depressed there was simply a steady 6 V DC on the horn ring. No superimposed AC waveform. In the old 6 V days there was no slip ring. The wire was just twisted as the steering wheel rotated. This would cause wear and ultimately the wire broke and the horn did not work, or the insulation wore thru and the horn blew when it shouldn't.


Chris:

On my Fluke 27 today I read about 3 megohms from one hand to the other. On DC voltage not much and very erratic, 20 to 100 millivolts. On my Simpson 303 VTVM I read about 0.3 V DC.

You have less salty hands than your friend.

I never had salt water problems other than maybe it caused failure of our main battery firecontrol radar. We did plow thru waves that went 40 ft over the bow and reached as high at that radar antenna. This meant the waves were 80 or so feet high. If you go half way up the superstructure in the following photo, then that is about were the top of the waves reached.
http://media-cdn.tripadvisor.com/media/photo-s/01/0f/0a/83/uss-wisconsin.jpg
The current photos do not show the radar antenna that we had. It was in the 150 megahertz range.

.
 

mivey

Senior Member
We did plow thru waves that went 40 ft over the bow and reached as high at that radar antenna. This meant the waves were 80 or so feet high.
Point A to point B sounds great but I would have voted for a path around the storm.:grin:
 

cadpoint

Senior Member
Location
Durham, NC
I beleive that it's call wicking, where the enviroment creates a path for electricity to flow on.
Salt water, and salt deposits are not your friend here...

Sound's like it's in the console of the craft!

As far as the mechanic, I can't disquailify him, I never got car disease. I'll beleive him, I'll even say he might have put the explaination into layman terms. I've seen where water has collected in a conductor. I do understand the rational parts of your statement! :cool:

You changing vocation's, Chris? :grin:
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
110530-1929 EDT

mivey:

It was a very large storm in the North Atlantic. We were headed to Scotland and did deviate far to the south before heading north again. The smaller ships went up and over the waves, but we had a destroyer escort with us that lost steering control and was going sideways over the waves. Large ships like ours plowed thru the waves. This is a function of wave wavelength and ship length. We pitched a few degrees, but took +/- 28 deg rolls.

Every gas bottle exposed to the waves was ripped from their mounting and I could hear them rolling across the main deck. Stairs, called ladders, were twisted like pretzels. I had access to the highest point in the superstructure, had a radar transmitter there, and so I was able to see the outside action. Had no problem with electricity, and everything was 60 Hz.

.
 
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