Seawater Ground- Necessary?

[thomm225]

A few years ago, I removed my diesel engine and replaced it with an outboard.

When I did this I also removed the boats seawater ground. All the grounds that went to the diesel now just go back to the battery negative post.

I have a DC System on my boat and really don't use Shore Power except direct hookup say to a wet vac or something of this nature

I also have solar panel and a controller charging my two 12 volt batteries that I have in parallel.

I did a little research online and got some conflicting reports as to whether a seawater ground was really necessary for a DC System ..... on a sailboat

[Stu Jackson]

I had your same setup on our Catalina 25 for the 13 years that I owned her. The battery (-) IS your ground.

[thomm225]

Originally Posted by Stu Jackson

I had your same setup on our Catalina 25 for the 13 years that I owned her. The battery (-) IS your ground.

Thanks.

That's how I have mine hooked up also, but I understand many believe you still need an actual ground for your system. (to the sea/earth)

I'm thinking it's okay like mine is now and yours was where it is basically floating and not grounded.

I'm not trying to get too technical but I saw it yesterday again when I was replacing a battery. I saw this thick negative side battery cable going down below to where the diesel used to be and remembered that I have a bolt through it's terminal with all the wires that did go to the engine for "ground" now going back to the battery directly through this cable with no earth/sea ground.

[KISS]

Originally Posted by thomm225

I did a little research online and got some conflicting reports as to whether a seawater ground was really necessary for a DC System

Me too. There's no consensus, but both sides seem to think that either set up is okay (they just argue about which is optimal). Personally, pending compelling information to the contrary, I'm going with a floating system (no ground).

[estarzinger]

Floating is the standard (smallish) aluminum hull solution.

There are some potential complexities with shore power and with HF radios, but it sounds like you are not too worried about either of those . . . .so it is all good.

[Hartleyg]

The common point at the battery in your boat is not "ground" per se, though the term is commonly used -- it's actually a "negative common point", which will work fine for you electrically.

There are only a few reasons why you might want to attach yourself electrically to the ocean via "grounding":
1) lightning protection for your electrical system, mast & metal rigging.
2) HF radio
3) corrosion protection

I doubt you have an HF radio, and unless you are in an unusual area, lightning protection probably isn't a big factor. Corrosion protection would only apply if you were connecting all your in-water metal bits together to protect them with a zinc anode - and this sort of system is more properly called "bonding", rather than grounding.
Since it seems you likely don't have any electrical stuff in the water (your outboard is normally out of the water, and it has it's own protections anyway) I feel you probably don't need to worry about "grounding" at all.

Hartley
S/V Atsa

[thomm225]

Originally Posted by Hartleyg

The common point at the battery in your boat is not "ground" per se, though the term is commonly used -- it's actually a "negative common point", which will work fine for you electrically.

There are only a few reasons why you might want to attach yourself electrically to the ocean via "grounding":
1) lightning protection for your electrical system, mast & metal rigging.
2) HF radio
3) corrosion protection

I doubt you have an HF radio, and unless you are in an unusual area, lightning protection probably isn't a big factor. Corrosion protection would only apply if you were connecting all your in-water metal bits together to protect them with a zinc anode - and this sort of system is more properly called "bonding", rather than grounding.
Since it seems you likely don't have any electrical stuff in the water (your outboard is normally out of the water, and it has it's own protections anyway) I feel you probably don't need to worry about "grounding" at all.

Hartley
S/V Atsa

I'm on the Chesapeake Bay which ranks second to Florida in the Lightning Strike Category.

I did a bit of research on lightning "protection" and read where some believe it's best NOT to give lightning a path to ground by connecting your lightning rod (your mast) to ground.

I was thinking about it some last week when I was on my "cruising" vacation

https://www.youtube.com/watch?v=6gcZKr25UUM

[Hartleyg]

Hi Jeff,

Cool! We're in Deltaville, VA for today & tomorrow, then we're Northbound again (CT, ME and NS this summer!)

If you are concerned about lightning, then connect your mast & chainplates to an electrode underneath - no need to involve your electrical system. When you had an engine & shaft, this was probably all the electrode you needed, but now that it's gone, you would need to add one. Traditionally, this was a copper plate, though other metals will work. An iron or lead keel is also good, of course.

You are correct, there is a lot of "controversy" regarding lightning protection - and there is a LOT of snake oil being sold out there as well. All I can say is I spent a lot of years doing lightning protection for mountaintop and building top radio installations, and bonding and grounding coupled with judicious use of surge arrestors was the ONLY thing that I've ever seen work consistently.

73 DE Hartley
S/V Atsa

[thomm225]

My point before was that many believe that you have a greater chance of being hit by a lightning strike IF your mast is grounded.

The research I did also indicated that Multihulls have twice the chance of being hit as a Monohull..............

And that larger monohulls with taller masts have a higher chance of being hit than a small monohull with lower mast

And that groups of sailboats together have a higher chance of being hit than one alone

I happened to think about all this after being under the thunder and lightning that was occurring over my head last week.........

[Hartleyg]

Well, Thomm, many people say many things - doesn't mean they're right -or wrong.

If leaving your mast ungrounded makes you feel better, by all means don't ground it.

73 DE Hartley
S/V Atsa

[thomm225]

Originally Posted by Hartleyg

Well, Thomm, many people say many things - doesn't mean they're right -or wrong.

If leaving your mast ungrounded makes you feel better, by all means don't ground it.

73 DE Hartley
S/V Atsa

It definitely doesn't make me feel better to not have it grounded, but lightning doesn't seem to care whether a boat is grounded or not since it will strike either

Any input is appreciated though....

Research shows that grounded boats get hit more often than ungrounded ones but that the damage to ungrounded boats is much worse

[misfits]

All my chain plates & mast are bonded to a keel bolt. All my thru hulls & shaft skeg are connected to the same bolt. My boat came that way from the factory. Way I see it if she got hit by lightning at least it doesn't give an insurance company a reason to tell you to go pound sand. You may want to research what if anything Bristol did for lightning protection/bonding.

Because I'm putting an electric drive in her my DC systems will end at the negative post of the battery. I do not plan on "grounding" the negative buss. The prop shaft will be isolated from the electric drive so the system has no contact with seawater. I am considering bonding the motor mount apparatus to the keel bolt for lightning protection. With that said I do plan on consulting with a very knowledgeable marine electrician to be sure I'm not shooting myself in the foot in doing so.

[thomm225]

Originally Posted by misfits

All my chain plates & mast are bonded to a keel bolt. All my thru hulls & shaft skeg are connected to the same bolt. My boat came that way from the factory. Way I see it if she got hit by lightning at least it doesn't give an insurance company a reason to tell you to go pound sand. You may want to research what if anything Bristol did for lightning protection/bonding.

Because I'm putting an electric drive in her my DC systems will end at the negative post of the battery. I do not plan on "grounding" the negative buss. The prop shaft will be isolated from the electric drive so the system has no contact with seawater. I am considering bonding the motor mount apparatus to the keel bolt for lightning protection. With that said I do plan on consulting with a very knowledgeable marine electrician to be sure I'm not shooting myself in the foot in doing so.

That's a good idea considering the insurance if you have full coverage as well as researching Bristol sailboats

I have liability only about $9.00 per month so I'm taking my chances there as well

I've seen no bonding on my boat and when doing the bottom a couple times no metal plates etc just thruhulls and the old raw water intake. I'll recheck that though down near the keel on the interior of the boat

I just noticed on a Bristol 27 Sales Brochure that it advertised:

(Grounded stays and wiring. Main sheet jam cleat. Topping lift. Sail slide gate. Flag halyard)

I'll check the stays and see where that wiring goes......hopefully it's not to where the engine used to be.