Bonding/grounding flexible shaft coupler

[LogoFreak]

Need some quick advice, I'm 10 days away from launching my boat and need to figure out the grounding. I have installed an r&d flexible coupling which breaks the continuity of electricity to sea water. R&D sells a silver impregnated rubber strip that one rolls up and installs inside the flexible coupling to re-establish the connection. I can do that or simply install a sintered grounding plate.

Which would be a better solution?

[waughoo]

Seems to me you would want a bonded shaft.  Ive seen a copper bushing mounted on spring steel that rides on the shaft and then has a grounding wire that goes to the block or the bonding system.  That said, your solution between the coupling seems simpler.

[dfloeter]

When we had a prop saver plastic thing in place I ran a short wire jumper from a bolt on one side to a corresponding bolt on the other.  It was simple and seemed to work. 

[Ron Hill]

Guys : I've had a flexible coupling for over 25 years and have not bonded it.  Just use one shaft Zn and have never had a problem!!

A thought

[LogoFreak]

Guys : I've had a flexible coupling for over 25 years and have not bonded it.  Just use one shaft Zn and have never had a problem!!

A thought

Ron, what do you use to ground your boat? How's the negative dc and green ac wire grounded to the sea?

[Jon W]

Right or wrong, I had viewed the prop shaft like a grounding rod driven into the earth to provide a ground for your house electrical system. On our boats, the system negative cable from the onboard electrical system connects to the starter/engine/transmission which in turn connects to the propeller shaft (grounding rod) that's in the water (earth). The engine/transmission are on isolator mounts. If a flex coupling isolates the connection from the drivetrain to the propeller shaft, how is connecting to the starter/engine/transmission grounding the boats electrical system? Maybe the bolts fastening the transmission flange to the propeller shaft flange provides the electrical connection to provide the ground?

I'm looking forward to hearing from the experts.

[Gregory M]

Logo
I have the same issue, deliberating between sintered bronze plate, wire connecting two bolts in coupler and "stuffing" R&B sels . I found this..     
https://www.marineoutfitters.ca/index.cfm?category=10002|11172&product=60463436&code=031669200357.
I'm not electrician either, but how about led keel via bolts as ground ? After all it is huge chunk of metal in water.

[KWKloeber]

The return electrical path

a lighting strike to "earth" via the shaft

Both the DC and AC systems are bonded to earth thru the AC ground/green shore power conductor (if your boat is ABYC compliant) or unless you have a galvanic isolator installed.

You can't possibly provide enough current carrying capacity for a lightning strike traveling down the mast to jumper to the prop shaft, and if it did along the way it may blow out the stuffing box/shaft log (strikes have blown out thru hulls.)

A faired and painted lead keel is a poor conductor to earth, but the bolts should ideally be bonded.

A bonded shaft is better than a non-bonded shaft (the more continuity in bonding and more sacrificial anode locations the better -- but everything is a trade-off.
Your Hx is similar to the shaft-- it's best to bond it, but if not and it's isolated -- the anode therein protects the "local battery" created by the different metals that are immersed in the electrolyte.

[Noah]

Maybe an expert(s) out there could explain the "necessity" for a bonded shaft? Wouldn't just having a shaft zinc and a HX zinc solve most issues that may be caused by a flexible shaft to engine coupler?

[KWKloeber]

Jon

Re: grounding rod.
Is your AC and DC separated?  i.e., not bonded?  Or bonded and you have a GI installed?

[Jon W]

No GI, and AC not connected to 12vdc negative buss if that's what you're asking. Main AC breaker is an ELCI I installed as part of my electrical upgrade in 2016.

Is a sea water ground necessary (per code or otherwise) for the AC and/or DC electrical system?

[glennd3]

You guys really lose me sometimes.

[waughoo]

If interested to catch up...

ELCI (Equipment Leakage Circuit Interrupter) Shore power breaker:
https://waggonerguide.com/elci-protected-shore-power/

GI (Galvanic Isolator):
https://shop.pkys.com/What-is-a-galvanic-isolator-and-why-should-my-shore-power-system-have-one_b_112.html#:~:text=A%20galvanic%20isolator%20is%20a,act%20as%20a%20giant%20battery.

[Ron Hill]

Guys : I'm not too sure exactly why you need or what a bonded drive shaft really does for a boat ??  Never had a problem without one???

A thought

[KWKloeber]

Jon

Ok. You're aware that's not abyc compliant?  The E-11 requires bonding the DC neg to the AC ground, whether or not there's an ELCI.

-k