Bonding/grounding flexible shaft coupler

[KWKloeber]

reasoning behind requiring the prop shaft provide an electrical path from inside the boat (either AC or DC or both), to the sea.

Noah

The DC has nothing to do with it.  The DC battery isn't referenced to earth as AC is, so connecting DC equipment to earth does basically nothing because there is no completed circuit.

As I said previously I feel it's best to bond as much together as possible (as practical) for the purpose of galvanic corrosion, then everything's at the same voltage potential, and if there's multiple anodes they act together.  But as I said the Hx (which will be a local battery due to the different metals immersed in electrolyte) will be protected by itself (by its own anode) even if the Hx is not bonded to the engine, etc.  However, it's best to bond the Hx (but most do not) -- so likewise a shaft (if having an anode) is protected even if not bonded (same as a strut.)   A strut oftentimes gets painted (or oxidized) and it doesn't make a really great earth ground, but if bonded it's better than not being bonded.
EVERYTHING once you step onto a boat are trade-offs and a compromises.

Now as far as AC, what I said before, the shaft can become a cattle prod and hurt/kill someone (even not in the water.) So is that better, or is it better to protect what's/who's aboard the boat?
If the shore cable loses the ground - Say something goes hot through a fault -- there's no ground to safely bleed it off.  But bleeding off thru the prop shaft turns that into the cattle prod.  It's possible that could continue for a long time without an indication of a problem.

If an ELCI is installed that's the best solution -- the threat of an undetected fault is VERY VERY VERY low, like near zero, then you won't turn the shaft into a hot prod.  Because that takes two actions -- losing the ground and the ELCI failing.

If no ELCI, one can at least install a $3.00 120v indicator light (like BlueSea, green indicating bond/ground) between the AC hot and ground -- as soon as you get on the boat you see that you have the ground connection.  (On yours it could be put near the main breaker.)
Note that testing a GFCI outlet DOES NOT test the AC ground.
Or one could keep a $5 outlet tester plugged in (which shows correct wiring, open ground, reverse polarity, etc.)

Caveat - that's not a "professional" opinion you sought -- it's a "practical" opinion -- because a professional must say "follow ABYC" (even if outdated and not making sense.)

[LogoFreak]

So I get that when plugged into shore power and as long as the marina is wired correctly I'm ok, but what happens if I add an inverter on board? Or bring my little Honda 2000 generator? Wouldn't it be necessary to have a ground to sea in that case in order to be safe? How does it affect swimmers around the boat? What are the potential issues?

[Ron Hill]

Guys : I'm not an electrical whiz nor idiot.  Your auto is a DC system like the boat and is not grounded !!

The only reasons that I plug unto shore power is :
1. to have the AC powered battery charger charge my DC batteries!! 
2. power my closed AC outlet circuits, so I can run an AC tool or an AC appliance.

I see no reason then to have the prop shaft grounded to the DC engine!!

A few thoughts

[lazybone]

I just realized why Mainsail has sworn off this one.

[KWKloeber]

Logo

This doesn't address your question per se re: the shaft but it is interesting in that it discusses the intricate nuances about grounding and what can go wrong if you're using a genset or inverter.

   

[Ron Hill]

Guys : I have used my Honda 1000 for years and so has hundreds of other C34s - especially those that use the East Coast ICW and the Bahamas!!! 
If your C34 is wired properly, you shouldn't ever have a problem with a generator or a properly installed inverter!! Regardless, if your drive shaft is grounded or not. 


A thought