Proper Boat Grounding

[dingbat]

so all grounding wires on my pontoon meet on an isolated buss bar, which is connected to my battery, which is connected to the motor.
if I'm wrong, speak up.

This is corect....

yep confusing......so, this is my common man explanation...pontoon.

12v DC
All powered equipment sends current out of itself when on. This current is negative (ground). This current needs to meet either at a grounding isolated buss bar or directly to the negative battery post or to the engine ground.
If I connect a negative return from a powered source to my "hull" , I am inducing current through my hull to ground. It'll take the least resistive path, which is to water. I'm inducing a potential current difference....two paths....one directly to the hull and the other from battery through motor/transom/prop.......since it is kinda confusing, just make sure all grounds are to the same final connection...battery/motor.....

Your 12VDC battery has the "potential" to supply 12.7 VDC supply and ground
Connect a 3" long wire and a 30' long wire to the positive terminal on the battery. Now measure the voltage at the end of each wire relative to the ground terminal on the battery.

With enough resolution, you'll find that the shorter cable has a higher voltage (potential) than the longer cable due to resistance of the wire,

Now measure the voltage on each cable using a "ground" other that the battery post. Say, between the short wire and the bus bar and longer wire to the bus in your helm fuse box.

bonding....just an example-

I installed my hot tub years ago so I needed to learn how.
AC high voltage high amps.
One requirement is that all touchable conductive structures touchable from inside the tub have to be bonded to the tub which is , of course, connected to the home panel. The home panel neutral and ground buss bars are "bonded " together in the panel. I have an aluminum gazebo right next to the tub. All structures are on a wooden structure. There is a "bonding" lug on the hot tub. So there is a bonding wire, think it's 4 gauge whatever the instructions required, from that structure to my hot tub.
Although my tub is GFCI protected, if my water was somehow energized and I touched that gazebo, maybe under a weird circumstance i could become the conductor......gazebo's mounted on wood, but not taking that
chance......so it's bonded to the tub which is connected to earth ground through my main panel....

In AC you have 3 wires, hot, neutral (ground) and earth ground.

The important thing to understand here is that neutral and “earth” do not play the same roles as they do in a DC circuit.

Hot and Neutral carry the power, but "earth" in an AC circuit serves as safety (bleed) valve in case of an imbalance of potential between hot and neutral legs of the circuit.

The excess (lost) voltage has to go somewhere. As such, all "earth" (bonding) wires are connected to what is typically a copper ground rod driven into the ground at the point your electrical service enters the home.

Connecting "earth" to neutral is just asking for problems...getting shocked

 

[jlh3rd]

but my neutral and ground bars are bonded in my home panel...required..if you have a sub-panel it is not to be bonded internally.
My home did not have the grounding rods as back in the day, they "grounded" to water pipes. I fixed that. And the rods are connected to the ground in the panel. So my "earth" is connected to the neutral...?...
not to get too off topic....

 

[Bugzilla46310]

bonding wires (Green or Green with yellow stripe) tie the hull, motor, zincs water, etc. to the negative side of the battery. they are there to tie them all together to the same potential for galvanic reasons. the potential between the ground terminal of the battery and the hull/motor/etc should be 0.00. this is to minimize corrosion.

grounding wires (black) tie the current paths from any electrical load back to the battery so you do not run current thru the hull. all loads must have a complete loop of power source to circuit breaker to load to ground.

the reason you do not want to run any current thru the hull is simple. it will galvanically eat the hull. if you attempt to use the hull as a current return to the battery, it will "work" for a little while, however your aluminum hull will look like it was soaked in acid after a very short period of time.

Excellent description!

 

[Scott Danforth]

Your pontoon chassis is all one assembly via welding and riveting.

 

[cyclops222]

All my Aluminum boat motors have a DIRECT negative connection. Between Aluminum hull and O B metal and motor transom safety bolts and nuts. Why starter motor has such big wires. Positive and negative to the battery posts

 

[bruceb58]

but my neutral and ground bars are bonded in my home panel...required..if you have a sub-panel it is not to be bonded internally.
My home did not have the grounding rods as back in the day, they "grounded" to water pipes. I fixed that. And the rods are connected to the ground in the panel. So my "earth" is connected to the neutral...?...
not to get too off topic....

You still need the ground to bond to the water pipe in addition to the grounding rod. In addition, you need a bonding connection between the hot side to the cold side and to a gas line(All usually done at the water heater) for current code.

Most people who put in ground rods, if they didn't have them before, put in two ground rods(spaced 6 feet apart minimum) since you have to have 8 feet of ground rod total.

 

[jlh3rd]

It is....2 rods.....if the hot/cold is bonded, I didn't do it.....no gas.

 

[JustJason]

Looked through some posts and some of the links in the sticky posts no longer work after a few decades! I think I know the answer but wanted to make sure. The wiring on my 1998 Sylvan 17’ Blue Fish doesn’t look up to my standards and I will most likely clean it up a bit in the spring and if any issues are found I will address those also. From what I see, the ground is never attached to the boat hull, like in a vehicle, but is isolated from the hull and only goes to the battery and related terminals. Is this a correct assumption? Thanks

ABYC E11 states 11.5.2.2 DC GROUNDING SYSTEMS AND BONDING - A metallic hull, or the bonding and DC grounding systems, shall not be used as a return conductor (see FIGURE 4A-B, FIGURE 5 , and E-11.16).

In a boat, for both corrosion and also electronic shock drowning reasons (if the boat also has AC power) the metallic hull is not the be used as a return conductor. In a vehicle there are not concerns, which is why you can use the metallic body of the vehicle as a return conductor.

 

[JustJason]

that is correct. except for bonding wires, you NEVER pass current thru the boat. it will literally dissolve from galvanic corrosion.

Electrolytic corrosion........

 

[JustJason]

umm....well, that's not what I'm finding after looking. My pontoon is DC only, but if this "grounding" to earth is through the motor/water/earth, then I can ground my negative any place on my aluminum structure. The motor is grounded to my transom so what difference does it make.
What about an RV.....a car.....
so just asking....

It will be easier to understand if you separate the word/term ground and give that 1 specific definition and then use a different term called something along the lines of return path to the source, which is different than the generic term of "ground".

 

[jlh3rd]

it's understood.....there's ground....and then there is grounding.....and "paths" (circuits)...and negatives (neutrals), and positives...and bonding.
However...my boat does not have to be in the water for my powered devices to work. So it does not have to be "grounded" through the motor/water/earth as someone mentioned. But the motor does connect the negative (neutral) path to earth ground , so it is "bonded" to ground just like my home's neutral (negative) is bonded to ground.
However, I could connect my battery's negative to my aluminum structure and everything should work....but I'm inducing a current path through the structure and highly inefficient.
The negative path is more like the "neutral" (white) in a house. The house does not have to be "bonded" to earth for devices to work either.

or something like this.....🫤
think we're done here.....I know enough to adhere to regs, wire a boat, hot tubs, panels, grounding, bonding, If things are done properly, potential charge differences take care of themselves.