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Bonding my Boat

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briang0

Regular Contributor
I need some advice on bonding

I need some advice on bonding my boat. I have an 8 gauge wire that is not currently connected to anything. Please tell me what it should connect. Does it go to all through hull metal pieces? After it connects all the through hull pieces then where does it go to the engine? Do I have to mount a zinc block on the outside of the boat and connect to it? I currently have zincs on the rudder and prop shaft. I appreciate the help.
 
"Brian here is a bonding chart

"Brian here is a bonding chart I made up for my boat. I hope it can help you.

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"
 
"Brian:

EJ's above exam

"Brian:

EJ's above example is a great start.
(any significance to the solid vs dotted lines EJ?)

All the metal should be connected thru that bonding wire. The engines usually have a free ground lug (around the bell housing) that is fine for this. The idea is to provide a low impedance path to minimize the galvanic potential that develops. Ideally, all the external metals will be of the same material.

If you have the zincs identified on and in good shape, that's usually adequate. A lot will depend upon the marina and your slipmates. The best way is to get an electrode and measure what you have. FastJeff has posted on an electrode previously but I can't tell you which section to search to find it."
 
Mark the dotted lines show the

Mark the dotted lines show the ac grounding route. The dotted line off of port side should be solid.
 
"EJ:

thanks for the answer.

"EJ:

thanks for the answer. Another item I questioned was the "earth ground" on the AC side, plug 1. That's not the same earth ground shown between the engines, is it?"
 
"That show the two engines gro

"That show the two engines grounded together. My lack of symbols.

The argument for keeping the grounds separate is that you don't want stray current from the shore power finding its way to your prop, rudder, thru-hulls, etc. If the safety ground on the dock had a potential of a volt or more it could lead to electrolysis on your boat.

The argument of bonding the DC and AC grounds together is that you can end up with an unintended connection between the two. Any device that has connections between both DC and AC power would potentially connect the two together. If you have two such devices then you can end up with some very interesting ground paths. While the AC ground should NOT carry any current under normal circumstances the DC current will.

In fact I believe this is what happened with another forum member frying his dc ground wire to a point that flashed fire the surrounding wood. If he wasn't there he could of lost his boat."
 
"I'm with you.

I just a

"I'm with you.

I just asked because w/o your explaining the details, a literal interpretation would mean the galvanic isolator was bypassed and after seeing some of your work i figured that wasn't the case. Of course that isolator mitigates the electrolysis issue and enables the "safety" feature of a common ground.

The last question on the schematic concerns the fuel tanks; did you bond them, too or the bonding inferred via the fuel caps?

tnx"
 
"<[img]"http://www.marineengin

"
284858.jpg


There is a ground wire that runs to a lug on the fuel tanks along with the 3/8 stainless line. Fuel fills have a ground wire at the clamp. Everything is tied into a massive 4" grounding bar. Everything that goes boom is bolted to it. You can't see the lugs welded onto the bar to the right. All grounds are a dedicated run either to this bar or the engine block.

This reminds me of the time when we were working on my brother-in-law's new 30 year old boat and unknown to us he was pulling his engine ground through the stainless braided fuel line. Trying to start it the braided fuel line started to heat up like a heating element to a point it melted the inner hose. I was down in the bilge watching all this from a birds-eye view. Flames jumped right out of that hose and I was screaming for the fire extinguisher. Like Sugarland sings, s@it happens."
 
"That's some set up....any

"That's some set up....anytime you want to practice or experiment, you can try it on my boat first, as long as it uses your stainless techniques."
 
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