Electrical current running through prop

[larry_arizona]

Was changing my prop and noticed a light electric buzz as I touched the prop.

This can't be normal?

I will add, it's only when the battery charger is plugged in.


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[zabooda]

Get a baseline of what is going on. Get an AC voltage reading from the prop to a good grounding pin at the outlet. Be careful as the full 120vac could be on the prop. The AC power cord could be grounded to some metal at attach points or where screws are used. Another area to look at is the charger itself. The 120Vac internally has connected to the 12Vdc ground either through chafing or a loss of the insulation on the dc ground wire (excessive loads in the past or excessive heat in the charger). Good luck.

[larry_arizona]

My guess is my building earth ground on the pole barn is compromised.

I am going to try plugging into house and see if I get the same buzz.

Also try a different extension cord.


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[zabooda]

In that case check your wiring at the receptacle. Harbor Freight has receptacle testers cheap as sometimes the wires are switched.

[HFarr]

My bet is you find an issue with your building too.

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[larry_arizona]

Plugged battery charger in from pole barn 0.15v at prop.

Swapped cord: 0.15v at prop
Ran cord from main house: 0.15v at prop.

Got me wondering if this is normal to have low voltage through the prop due to engine is the ground in a boat?


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[HFarr]

Just curious, but have you tried grounding your boat since it's on the trailer and not grounded? Not that that would make a difference in whatever is causing the prop to receive any current. But it may redirect that voltage enough so you don't get a shock from it. Maybe clip a jumper cable to the block and a piece of metal stuck in the ground. Just a thought.

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[HFarr]

We had a contractor nick a 480 volt power cable with directional bore machine a few years back. Small nick and nothing tripped out anywhere. The next few days, we had kids reporting they felt "static" shocks between the grass and concrete slab that a metal shelter was mounted to when they were sitting on the edge of the slab. They thought it was cool. We couldn't figure out what was causing it. The directional bore was at least 1,000 yards away. And of course, they said their machine had alarms that would have alerted them the minute they even got close to power. The next day the chainlink fence on the opposite side of our football field would light you up like an electric fence if you touched it! Then within a couple of hours, a line fuse on a power pole blew. Power company could not reset it because it would immediately blow. So they checked behind the boring company and dug up the nicked cable they claimed they never got close to. It had
slowly burned that nicked jacket into a dead short. All of this to say, open shorts can show up in strange places and do funny things.

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[larry_arizona]

I have not run the boat to ground from the trailer.

I can try flipping battery switch on to see if I get voltage off the prop next.


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[zabooda]

0.17 volts is hardly anything. It is probably an ac component from the dc charger. Battery chargers are notorious for their poorly filtered dc output. Mainly to cut costs and batteries don't care. They are an infinite load to the charger. Check out half wave vs full wave rectification. Half wave is often used for batteries while full wave are like electronics power supply with very little ac component.

[larry_arizona]

Measured with charger unplugged

Bat1 on: 0.147v
Bat2 on: 0.147v
Bat off: 0v
Charger on: 0.154v

Definitely the boat ground, just don't know if this is normal.


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[Holdmybeer]

0.15V on a fiberglass insulated boat is hardly nothing. However, leave your switch on and your battery(s) will be dead in a month.

I wonder if you have a loose ground wire from the batteries to the bus bars. 2yr old boat might have had a bolt vibrate loose. I have had 1.5 loose turns on a car battery ground prevent it from starting.

[larry_arizona]

0.15V on a fiberglass insulated boat is hardly nothing. However, leave your switch on and your battery(s) will be dead in a month.

I wonder if you have a loose ground wire from the batteries to the bus bars. 2yr old boat might have had a bolt vibrate loose. I have had 1.5 loose turns on a car battery ground prevent it from starting.

Switch is always off in barn. But I will start chasing loose connections


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