Grounded or ungrounded boat?
- Thread starter Borbeck
- Start date
Welcome aboard SBO, @Borbeck. The “boat” is grounded if the hull is made of steel or aluminum, and the hull is electrically bonded to the negative battery terminals. (Generally, the house bank and the engine start bank are bonded together on the negative poles). Composite FRP and wood boats are considered grounded if the engine block and metal thru-hull fittings (and keel) are bonded to each other, and DC ground. It’s very easy to spot these bonding wires or straps if you look at the inside of the fittings. From the outside of the boat (if it’s on the hard) you can use an electrical continuity checker to see if any 2 fittings are connected.
FWIW, I don't see the need for bonding the thru-hulls. Volvo-Penta isolates their marine diesels from ground, and only momentarily connects the block to ground during start/stop operations to actuate the starter or stop solenoid. They also isolate the prop shaft and tout that design as an anti-electrolysis measure.
With a meter against a known earth ground. Grounded and bonded can be not the same thing but are often spoken as if they were even though we all know that a negative battery terminal is not an earth ground.
Not on all Volvo Penta engines.
My OEM starter is always grounded to Negative Battery terminal, thus the Engine body is too. The starter is bolted to the engine.
Thus, the need to use Shaft Zinc, connected to the engine, to prevent Galvanic Corrosion.
In addition, per ABYC standards, a #10 Green/ yellow stripe wire, grounds it per Lightning standards. [ABYC now includes that in E-11]
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@Borbeck you boat is normally not grounded when on it trailer. Why is that important? Lightning strike reduction.
When in the water, metal in the water needs to be grounded and galvanic corrosion protected.
The term Grounded, for boats in water, means that your submerged metals are at the same electrical potential as the surrounding water.
We use Zero Volts DC of a Neg terminal, of the on board battery , normally.
Jim...
I do not have an engine. I am worried about lightening. I am making a camper out of my boat. I have no paper work on my boat.
I was not given any factory paper work on my boat when I took possession of it. I am restoring it completely and do not want to have it damaged.
I assume you are camping with the Mast Down.
If so, your boat is isolated from Lightning, if the trailer front tongue wheel is put on something non conductive like a 4x4 block of wood, old Ice chest lid, or cinder block.
Sometimes you can use your trailer spare tire too, if easily removed.
Also you can leave it hooked to the car, no trailer chains dangling to the ground.
Isolate yourself, boat and car, during Lightning storms
Jim...
PS: Welcome to SBO and people can help with most anything, including your boat paper work. Find your HULL ID #, normally a small metal plate on Starboard outside.
If so, your boat is isolated from Lightning, if the trailer front tongue wheel is put on something non conductive like a 4x4 block of wood, old Ice chest lid, or cinder block.
Sometimes you can use your trailer spare tire too, if easily removed.
Also you can leave it hooked to the car, no trailer chains dangling to the ground.
Isolate yourself, boat and car, during Lightning storms
Jim...
PS: Welcome to SBO and people can help with most anything, including your boat paper work. Find your HULL ID #, normally a small metal plate on Starboard outside.
Most boats without inboard engines do not have their electrical systems grounded because there is no ground, which is the engine. The battery negatives simply tie the batteries together. With an inboard, the battery negatives go to the engine. That's pretty much the only major difference.
Bonding and grounding are two separate issues. That's why they are spelled differently and mean different things.
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