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Old 21-12-2018, 18:05   #16
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Re: grounding thu hull fittings . ??

My first boat had the through hulls bonded. When the bonding wire corroded along with a ground wire the current out the fitting. The only thing the kept the boat from sinking was caulking.

Im definitely in the dott bond camp. It makes little sense to me to hook anything electrical into non electrical systems.
It is OK if others want to do it different on THEIR boat
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Old 21-12-2018, 21:54   #17
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Re: grounding thu hull fittings . ??

following....all are thruhulls are bonded (factory). And since our boat was designed and built for Asia/EU power (230v, 3-wire) we recently installed a Victron auto selecting iso transformer.
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Old 23-12-2018, 08:30   #18
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Re: grounding thu hull fittings . ??

Hey Cruisers.

We have the same model/year boat as Orion Jim (Cape Dory 31, 1984) with the same factory installed bonding/grounding system. We cruise in northern New England and the Maritimes where lightning strikes are not as common as in warmer climes.

So, we're curious if any Cape Dory owners with boats of the 1984 vintage, or other boats with similar bonding systems, who cruise in Florida or further south have had lightning strikes. Any comments welcome.

And a very Happy Holidays to all.

Jenn and Terry
Jenn & Terry
North Conway, New Hampshire
Mahone Bay, Nova Scotia
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Old 24-12-2018, 10:54   #19

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Re: grounding thu hull fittings . ??

"Ground?" Sure, makes sense - as long as you don't think about it!

Except when connected to shore power, "ground" is a misused term on boats. Seawater isn't copper: it's conductivity is very low. Stick ohmmeter probes in it and see for yourself. It's better to think of a boat like an aircraft in flight. Want a "ground"? OK.

  1. fill a bucket with dirt,
  2. stick a copper rod in it,
  3. and call it "ground."
It'll be completely useless, but if it makes you feel better...

In AC power distribution to homes, one side of the mains supply is connected to an actual earth potential (neutral) just outside the home for lightning protection. In the early days when AC power floated above ground, people objected to having lightning flying around in their homes (side strikes).

The correct term is "common," short for "common potential." But people long ago confused "common" as a ground - first in automobiles (which are, because of their rubber tires, insulated from earth potential) and the term got stuck with people who didn't have an electrical background.

Connecting all conductive objects to "common" (including, by convention, the battery negative terminal) prevents, or at least reduces, a destructive "side strike" if the vessel is struck by lightning. Side strikes (also known as "sideflashes") start fires.

A description of the rationale is described in National Fire Protection Association standard NFPA 780: It has a section specific to vessels. You have to pay for that document; here's a similar free document:

Preventing galvanic corrosion is a separate, and much more complex, topic.
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Old 15-05-2021, 03:46   #20
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Re: grounding thu hull fittings . ??

Hi All,

I own a Wauquiez Centurion 32 from 1978. It has a new engine, volvo penta d1-30, installed in 2009. I purchased the boat in 2019. I noticed that the engine mass is connected the the bronze thru-hull via an electrical wire. It is the only one that is connected to the engine mass. I cant find an explanation for it. Picture here.
It has been installed by the Volvo dealer. I dont understand the purpose of it and would like your views if I should keep as is or remove that wire...Thanks all!
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Old 15-05-2021, 03:58   #21
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Re: grounding thu hull fittings . ??

Greetings and welcome aboard the CF, Mahells.
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

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