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Bonding and Grounding of Underwater Metals

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5.7K views 14 replies 9 participants last post by  Lantau  
#1 ·
Can anyone advise how all their below waterline seacocks, through-hulls, and other metal elements are bonded? In theory they should all be bonded with minimum 8AWG cable and all that should be tied to the DC ground bus or negative engine terminal. Not sure mine is quite like that and am trying to figure out what the factory baseline configuration is.

Thanks,
Ryan
 
#2 · (Edited)
Hmm. Can of worms. I think think this is one of those questions that you'll get different opinions on. I think most of your fittings should NOT be bonded together (they should be kept isolated). How's that for disagreement already? It depends on what you want to do it for. Is it for protection from a lightening strike or to prevent corrosion from stray current in the boat or from stray current in a marina? These require different approaches, but I think none results in bonding everything together. For example, if it's lightening you're worried about (to protect you if not your electronics, which can probably only be protected by the gods), you'd want to bond things near the mast. If boat current is a problem, fix the problem. If marina current is the problem, bonding everything could just make it worse. Unless a previous owner has changed something, your boat may be bonded appropriately right now. Don Casey's boat fixing book has a section on this sort of thing. But, again, I think you are going to get different perspectives on this. (Like my recent question on lifelines: some say wire, some say rope, and never the twain shall meet.) As for my 37, which I'm confident is still 'bonded' as it was from the factory, almost all of the underwater fittings are NOT bonded together.
 
#5 ·
I guess my specific question is: How is your Pacific Seacraft bonded?

The professional marine community very clearly articulates the need, and requirement for, bonding of underwater hull elements. It's a safety issue; everything on the boat should be at the same potential. This is an ABYC (American Boat and Yacht Council) requirement for yachts and motor boats, a US CFR (United States Code of Federal Regulations) requirement for passenger and commercial vessels, and a design and operational requirement for vessels of the U.S. Coast Guard and U.S. Navy.

I'm not terribly concerned about the lightning protection, save for the fact to increase the bonding wire size from 8AWG to 6AWG where bonding conductors are installed as a secondary or parallel path for the main lightning conductor.

Ryan
 
#3 ·
If lightning is your concern then there is no scientific research that proves that a bonded boat is better protected than a non bonded boat. It is difficult to set up controlled experiments with 10,000,000 volts of electricity.
Anecdotally, non-bonded boats do not get hit as often as bonded boats but bonded boats may be able to survive a lightning strike with minimal damage.
 
#4 ·
A description of the PSC 34 ground systems is in the PSC 34 Owner's Manual. I assume a description of the ground systems is also in the PSC 37 Owner's Manual.

If you don't have a copy, you can Google the Pacific Seacraft 34 Owner's Manual; perhaps the 37 systems are similar/identical.

Bill Murdoch
1988 PSC 34
Irish Eyes
 
#8 ·
Ryan,
Without wading into the discussion about what is "right", I will offer at least one data point: Our 1983 Pacific Seacraft 37 has no bonding and I believe this is original. All seacocks are isolated, .i.e. no bonding wires. We do have lightning ground cables that run from the chainplates and mast to a dynaplate. The Keel is not bonded electrically to anything.
Our bronze seacocks are all original (Groco model SV with rubber plug spool) and in good working condition with no dezincification visible on valves or thru-hulls.

Dave
Crealock 37 #151
"Eowyn"
 
#15 ·
This sounds more or less like my 2004 PS37, but like some others who have commented, I have one or two seacocks connected (the only one I can recall is the raw water intake, which is wired up but I don't know exactly to what), and I have the separate SSB grounding strip (incredibly long thing surrounding the boat). I think the mast is connected to the keel stub via the keel bolts beneath the mast post. But, just to be clear, almost all of my seacocks are not bonded together (rubber hoses to each, so they are isolated).
 
#12 ·
The "recommendation" has more to do with "if installed" the E-2 guidelines should be followed. It is not a requirement/recommendation to install a corrosion bonding system just that if the builder chooses to do so E-2 is a guide as to how to do it correctly and if you choose to do so the ABYC suggests following the E-2 guidelines..

I recently had a case where a Canadian surveyor insisted cathodic bonding was a requirement under ABYC and the US insurance company wanted it installed. I had to go to battle for the customer and no cathodic bonding is NOT a requirement under ABYC and yes the insurance company finally agreed that it was not....