Electricious

[tolong]

I need some help. I have a alumniun hual boat and the hual is grounded can some one tell me if that can cause electricious on the boat? If I disconnect the ground at the motor the 12volt reading goes away should
the outboard motor be ground to the haul? The volt reading I is 12 volts from the poitive post on the battery to the boat haul.
Thanks the help

 

[imported_knightgang]

Re: Electricious

Your electrical system should not ground back to the hull. All of the electricals in the boat should ground back to the negative battery terminal.

 

[RickJ6956]

Re: Electricious

Your electrical system should not ground back to the hull. All of the electricals in the boat should ground back to the negative battery terminal.

Forgive me for disagreeing, but that's not necessarily true. There are many different wiring schemes. Most do indeed use the engine or the hull as a ground instead of the battery.

 

[HappierWet]

Re: Electricious

I am not sure that we are discussing the same phenomenon. What I think you are asking about is ELECTROLYSIS which is an occurence of electrical current being passed thru two or more dissimilar metals.
Personally, I believe grounding accessories thru a metal hull to be a bad practice and would never buy a boat where I observed it. This would be even more extreme in a high salinity environment. Evidence of electrolysis could include corrossion, scaling, and pitting.

 

[jdlough]

Re: Electricious

I had a wood skiff last year. An old rental boat. The oarlocks were installed with DRYWALL SCREWS!

Yep, that worked real good when the motor died and we tried to row back home.

The screws acted as sacrificial anodes for the oarlocks, and were dissolved to dust.

 

[tmfd]

Re: Electricious

I had an wood skiff last year. An old rental boat. The oarlocks were installed with DRYWALL SCREWS!

Yep, that worked real good when the motor died and we tried to row back home.

OoooooooooooKaaaaaaaaaaaaay

 

[Splat]

Re: Electricious

Unlike the wiring in your car, the hull of your boat should not be used as a ground plane.

Bill

 

[Cofe]

Re: Electricious

Electrolysis is a electronic effect caused by a liquid moving by its surface. Note that most boats have sacrificial anodes on them to minimize the effect. And yes many boats are grounded to the frame. Inspect you're anodes especially in salt water conditions, replace them when they get wore down or fall off. Or the the electrolysis will start working on the metal parts of your boat. Signs of electrolysis is "pitting" on the metal.

 

[5150abf]

Re: Electricious

Concur, a boats electrical system should be closed loop not open ground and yes that can cause electrolosis but really only if the boat stays in the water for a long period.

If you trailer your boat it shouldn't cause a problem.

I have seen some toons with that, kinda like little piles of white powder all over the place.

 

[Silvertip]

Re: Electricious

The very minute you bolt an outboard to an aluminum boat you have grounded the hull whether you want to or not. The negative battery cable is bolted to the engine block. Bonding straps are provided across any rubber isolating mount and bushing to ensure a good ground is achieved between those assemblies and the engine block. The net result is the hull is at ground potential. The "quality" of that ground depends on how much paint is separating the bolts from the engine and the hull. That however, does not mean the hull should be used to ground things. It definitely should not.

 

[This_lil_fishy]

Re: Electricious

The very minute you bolt an outboard to an aluminum boat you have grounded the hull whether you want to or not. The negative battery cable is bolted to the engine block. Bonding straps are provided across any rubber isolating mount and bushing to ensure a good ground is achieved between those assemblies and the engine block. The net result is the hull is at ground potential. The "quality" of that ground depends on how much paint is separating the bolts from the engine and the hull. That however, does not mean the hull should be used to ground things. It definitely should not.

Uh, yup. (to steel a term somewhat). Only difference would be a small outboard mounted to a wood transom on a metal boat. Then it would not ground to the hull. Can't see how any aluminum hull would not be grounded via the motor otherwise.

Ian

 

[HappierWet]

Re: Electricious

Yes, You are right about having a Ground Potential when an outboard is bolted onto an aluminum transom. However, That does not equate to having current passing thru the hull. The reason being that there is nothing for a positive potential. What I mean is that it is only one side of the circuit.

 

[RickJ6956]

Re: Electricious

The boat itself is the "positive potential", or more specifically, its ground is at higher potential than the surrounding water -- which is at earth ground.

Think of it in terms of two 12-volt series-wired batteries that give you 24 volts: The first battery's negative is connected to the second battery's positive. The second battery's ground is actually zero volts. The first battery's negative is actually at +12 volts. The boat is the first battery (although the currents and voltages are quite a bit lower).

The second part of this is the electrical current set up by dissimilar metals. The aluminum in a boat or motor will react with a steel piling or zinc. Water, like the wires in an electrical circuit, becomes the conductor. Anywhere there is exposed metal there will be electrical current and the resulting corrosion.

 

[jonesg]

Re: Electricious

From what I've read, the battery power system should be a closed loop.

But all the major metal parts should be grounded to each other to "spread the galvanic load" or effect of electrolysis, so no corrosion becomes concentrated in any one particular area.

The Green wire used in many boats is for such purpose, called the bonding system , it shouldn't be connected to the power system ground.

http://www.yachtsurvey.com/ElectricalSystems.htm

 

[Cofe]

Re: Electricious

Not to change the subject,,,,,
One guy brought his outboard in, and the anode that is on the leg had a pile of metal bolted onto it. I asked him what that was for, and he said he added to the weight that's there, because his motor kept popping up when in reverse.
He laughed and laughed when I showed him the reverse lock.

 

[tolong]

Re: Electricious

Thanks to all for your help. I took the boat back to Y Marine in Oregon and they made me one heck of a deal on a new hewescraft so I took the deal
Thanks again
Tolong

 

[RickJ6956]

Re: Electricious

From what I've read, the battery power system should be a closed loop.

It is, except for all the points of contact with the water. Those points of contact will bleed "trickle currents" through the engine, drive, and especially an aluminum hull. The trickle currents are what cause the corrosion. You can't stop it. All you can do is slow it down with the proper protective coatings.

Galvanic isolators are standard issue for the grounds on most boats with shore power. Essentially they are a pair of reversed-biased diodes that don't turn on with trickle currents to activate the galvanic corrosion. They isolate the boat (water) ground from the shore power's ground.

They also protect the people on the boat by shunting higher currents to ground instead of frying humans.