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Old 09-18-2020, 09:35 AM   #1
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Bonding System - Engine too?

Re-doing the electrics on my Willard 36, including the Bonding System. Running #6 Ancor wire for enhanced lightning protection.

QUESTIONS:

1. Do you run a drop to the engine and/or transmission? Engine is a Perkins 4.236 NA with Velvet Drive transmission. I have a shaft-brush to ride on my 1-1/2" bronze shaft.

2. Best way to tie-in a 'drop' to each protected thru-hull? I read Steve D'Antonio's article on bonding basics (I can't get the link right now) and he strongly recommends not to 'hop' from thru-hull to thru-hull in series due to resistance, but rather to have a central run of conductor (preferably copper strap, but will be #6 wire for me) with 'drops' to each thru-hull. The only way I can think to minimize resistance when joining a drop to a cable is to strip-away a couple inches of insulation on the central-run cable, then solder-in the 'drop' cable.

Am I over-thinking this? Other thoughts?

Peter
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Old 09-18-2020, 09:44 AM   #2
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The engine block is usually bonded to the same place that the DC ground is attached for the starter/alternator circuit. With that you don't need your shaft brush unless you have a Drivesaver which insulates the shaft from the transmission/engine block.

I think Steve is being too pure. I would just series daisy chain the bonding grounds to the thruhulls. Stripping the main bonding wire and soldering a drop is a kludge IMO. Doing with with T crimp connectors adds even more resistance and defeats the whole purpose of drops.

David
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Old 09-18-2020, 09:50 AM   #3
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Steve D knows much more about this than I do, but I am wondering if he doesn't like them in series because if one gets disconnected, the other connections are also out of commission. However, a boat owner who checks them periodically, it's not an issue.
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Old 09-18-2020, 10:10 AM   #4
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My sense is the Steve D article (which has a server-error on the link) is concerned about resistance and such for lightening protection. I would think that for pure bonding, heavy cable and ground straps would not be needed.

I do recall the thought behind the shaft brush being connection via the transmission and engine isn't always great.

Peter
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Old 09-18-2020, 11:25 AM   #5
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Brushes on the shaft are recommended because the shaft coupling may not be electrically perfect.
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Old 09-18-2020, 12:23 PM   #6
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My MT had all the bonding removed during its resto. I was not going to reinstall the bonding until I saw how fast the anodes were being wasted away (they were too small to begin with). I re-installed a limited bonding system. I ran SS ground strapping to a bus bar from the newly installed aluminum divers dream I had installed. From there, it is all individual 8-gauge runs to both shafts (brushes), rudders, rudder stuffing boxes and struts. All of my thru-hulls are isolated due to being connected with rubber hose only and being of only single metal construction. Unless the metals are connected somehow, they are out of the equation entirely. The resistance reading between my shaft and the trans is 50-ohms. The engine/trans is isolated as far as a ground bonding system is concerned and is not interacting with my new bonding system. My electrical system is still bonded through my motors and batteries. Extra protection from stray voltage on my dock power inputs with quality isolators (just in case a ground is made somewhere by mistake).



That's it. Using a Ag/AgCL reference anode, my protection is a constant -.9v. Spot on for brackish water
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Old 09-18-2020, 07:24 PM   #7
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Daisy chaining I believe is not recommended because of ever increasing resistance from corrosion.....otherwise it wouldn't matter.
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Old 09-19-2020, 07:58 PM   #8
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Run the main conductor to 100A bus bars strategically placed near a cluster of underwater metal components. Run whips from the bus bars to the individual metal. Don’t daisy chain. Shaft brush is not useless but nearly so. I would recommend not using it.
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Old 09-19-2020, 08:12 PM   #9
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Wouldn't the use of zincs in the cfresh water ooling systems indicate that the engines/generator are sensitive to electrolysis and benefit from additional "bonding"?
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Old 09-19-2020, 09:07 PM   #10
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I put a couple of bus bars in strategic places near to a lot of bonding points. I run the main wire to the bus bar and then go from the bus bar to each bonding point. I cleaned up the port side last winter when that engine was out. This winter ai will do the starboard side wen I pull the starboard engine. One of the things I didnít like about the current setup was that the bonding wire would come in on one bolt of the strut backing plate and then go out on a different bolt on the backing plate effectively making the backing plate part of the circuit. I guess they did this to save the 8Ē of wire. They did this all over the boat on things like the rudder stuffing boxes. I am changing it so that the in and out wire goes to one bolt so the item doesnít become part of the circuit.
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Old 09-20-2020, 01:01 PM   #11
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@Swfla #9
A bonding system is primarily installed to keep all of the underwater bits at the same potential which will alleviate own boat induced stray current corrosion since there is no potential difference between the underwater metal bits.

If the bonding system is then connected to a hull sacrificial anode, the anode can provide cathodic protection current to all the connected metal components if it has enough surface area.

For galvanic corrosion or beneficial cathodic protection to occur, there needs to be three components present: two or more dissimilar metals, electrically connected, and immersed in the same electrolyte.

The electrolyte in the engine is not the same electrolyte that the vessel is floating in as galvanic (or CP) current will only be effective a couple of diameters into a pipe or annular space. This is why the engine FW/SW heat exchanger has an anode installed on the SW side.

By the way, electrolysis is the dissociation of water into hydrogen and oxygen or is something that is done at the beauty parlor to remove unwanted hair. :-)
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Old 09-20-2020, 03:22 PM   #12
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primarily. good shop talk about the subtle difference.
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