Wire schematic help

[Tbmyer88]

UPDATE*
Took the boat out last Saturday. Had her cruising about 28mph up the river next to my house and had an alligator launch off the bank under to boat and take out my lower unit. SMH….
B. O. A. T.

 

[KMixson]

UPDATE*
Took the boat out last Saturday. Had her cruising about 28mph up the river next to my house and had an alligator launch off the bank under to boat and take out my lower unit. SMH….
B. O. A. T.

I have not hit them while under power but have had them rub up against and bump the bottom of the boat while anchored.

 

[Tbmyer88]

I have not hit them while under power but have had them rub up against and bump the bottom of the boat while anchored.

Me neither, until now. Motor jumped out the water and shut off immediately and started smokin. Trim and tilt work work now either.

 

[MDCrappie]

FWIW I have NEVER, EVER had any boat with a ground to the HULL! Especially any TIN boat ... but what do I know, I've only wired 20-30 boats ...

So what happens when an electric start outboard is bolted on the TIN boat? Isn't the hull then "grounded" to the starting battery? What issues would "grounding" the hull cause?

 

[LDUBS]

From what I read there is confusion with current flow over the DC positive and negative wires versus bonding via the outboard. If there is agreement, and there should be, that we don't want current flow through the hull, then what would be the reason to purposely connect the battery negative terminal to the aluminum hull.

 

[GTS225]

I'm in agreement with Ldubs on the no current through the hull thing. I know that there's a magnetic field generated around a wire when there's current flow, so it would be the same through a boat hull, just not as concentrated. I can only speculate on how it might affect your depth/fish locator or onboard compass. It may also have some affect on corrosion problems, especially in a salt water environment.

Roger

 

[MDCrappie]

From what I read there is confusion with current flow over the DC positive and negative wires versus bonding via the outboard. If there is agreement, and there should be, that we don't want current flow through the hull, then what would be the reason to purposely connect the battery negative terminal to the aluminum hull.

I'm in agreement with Ldubs on the no current through the hull thing. I know that there's a magnetic field generated around a wire when there's current flow, so it would be the same through a boat hull, just not as concentrated. I can only speculate on how it might affect your depth/fish locator or onboard compass. It may also have some affect on corrosion problems, especially in a salt water environment.

Roger

I'm not talking of using the hull as a ground. I'm against that too. ALWAYS run the negative part of every circuit back to the battery using wire, never "using" the hull. But grounding, or I think more correctly "bonding" the hull is a good idea.

LDUBS = what "purposely connecting the negative to the hull" on a properly wired boat will do is prevent the boat itself from becoming the "positive" in a circuit with the outboard, which with an electric start one we know is directly connected to the negative.

 

[LDUBS]

I'm not talking of using the hull as a ground. I'm against that too. ALWAYS run the negative part of every circuit back to the battery using wire, never "using" the hull. But grounding, or I think more correctly "bonding" the hull is a good idea.

LDUBS = what "purposely connecting the negative to the hull" on a properly wired boat will do is prevent the boat itself from becoming the "positive" in a circuit with the outboard, which with an electric start one we know is directly connected to the negative.

Admittedly, my knowledge is very limited, so I'm kind of sticking my neck out here - Lol. If we are talking about the outboard creating a bond to the hull as opposed to grounding the battery to the hull, then I think we are saying the same thing. Otherwise everything I read says not to ground the battery (-) to the hull on an aluminum boat. Neither of the aluminum boats I've owned did this. Same is true of my trolling motor battery. It is a free floating system with no direct connection from the battery (-) to the hull. I guess my question is if it were a best practice, then why isn't it commonly done.

 

[MDCrappie]

Admittedly, my knowledge is very limited, so I'm kind of sticking my neck out here - Lol. If we are talking about the outboard creating a bond to the hull as opposed to grounding the battery to the hull, then I think we are saying the same thing. Otherwise everything I read says not to ground the battery (-) to the hull on an aluminum boat. Neither of the aluminum boats I've owned did this. Same is true of my trolling motor battery. It is a free floating system with no direct connection from the battery (-) to the hull. I guess my question is if it were a best practice, then why isn't it commonly done.

Can you direct me to what you've read?

With this "free floating"system what happens if one of your positive wires gets chaffed and makes contact with the aluminum"? In my boat if this happens it blows a fuse and I know there is a problem. In your boat nothing will likely happen with the electrical system at all. Now put your boat in the water and leave it there for a couple hours.
Without the fuse blowing (since the hull is not bonded to the negative) your boat hull essentially becomes the positive. Your motor is grounded so it is the negative. Once in the water current will flow and guess what becomes the sacrificial anode

 

[user 26281]

Can you direct me to what you've read?

Now put your boat in the water and leave it there for a couple hours.
Without the fuse blowing (since the hull is not bonded to the negative) your boat hull essentially becomes the positive. Your motor is grounded so it is the negative.

First, think your on the correct track.

A tin boat should not use the hull as a return (current) path for 12vdc. Meaning no (-) wires back to battery, but instead the (-) wires are connected to hull, using the hull as the return path. Like early cars.

When using a copper return wire, even if you connect battery (-) to the hull, the copper wire return path is going to have less resistance than alunium, and virually no current flow through the hull. Except, if something happens to the copper wire and the aluminum becomes the path of least resistance.

Your correct about the starter battery, motor, and hull being grounded. They are at a 0v potential, but they are not at earth ground potential until the boat is in the water.

I don't belive the hull can ever be positive when in the water because it is at earth ground potential.

 

[MDCrappie]

Your correct about the starter battery, motor, and hull being grounded. They are at a 0v potential, but they are not at earth ground potential until the boat is in the water.

I don't belive the hull can ever be positive when in the water because it is at earth ground potential.

Exactly how it should be. Now if the motor (which is grounded) is not "bonded" with the hull then the potential for the hull to become positive IS there. Once the hull is positive and the motor is grounded the current will flow thru the water and eat away at the aluminum where it touches the water. The hull WILL become the anode.
Now if the hull is bonded to the motor (which is grounded) this will never happen because as soon as the positive wire contacts the hull the fuse will blow breaking the circuit.

 

[user 26281]

So what happens when an electric start outboard is bolted on the TIN boat? Isn't the hull then "grounded" to the starting battery? What issues would "grounding" the hull cause?

In most cases your correct. Paint, rubber transom pads may prevent some batteries from being tied to hull ground trough the motor, but most are tied to hull ground.

Can't address what it could cause, but my boats is a 1980 and have always had the starter battery grounded to the hull through the motor.

 

[user 26281]

Exactly how it should be. Now if the motor (which is grounded) is not "bonded" with the hull then the potential for the hull to become positive IS there. Once the hull is positive and the motor is grounded the current will flow thru the water and eat away at the aluminum where it touches the water. The hull WILL become the anode.
Now if the hull is bonded to the motor (which is grounded) this will never happen because as soon as the positive wire contacts the hull the fuse will blow breaking the circuit.

Probably disagree more with how it is said, than what is meant.

A tin boat with no paint is at earth ground potential when in the water, even with motor up, mounts not touching the water, and no bonding to the hull. The motor and battery, since it is not in contact with the water is at 0v potential from - battery terminal. The motor, in this case is more positive in respect to the hull, because the hull is at earth ground potential.

They may be at different potentials in respect to each other (This is why you bond at 250milli ohms), cause current flow, but the hull is still at earth ground potential, the ultimate 0V.

 

[MDCrappie]

Probably disagree more with how it is said, than what is meant.

A tin boat with no paint is at earth ground potential when in the water, even with motor up, mounts not touching the water, and no bonding to the hull. The motor and battery, since it is not in contact with the water is at 0v potential from - battery terminal. The motor, in this case is more positive in respect to the hull, because the hull is at earth ground potential.

They may be at different potentials in respect to each other (This is why you bond at 250milli ohms), cause current flow, but the hull is still at earth ground potential, the ultimate 0V.

I'm thinking you are an A/C voltage guy? That's where our terminology is getting crossed. Just because the tin hull is in direct contact with the water (or earth) it does not mean it's at 0 voltage potential. The earth is not the "ground" in a D/C system like it is in an A/C system. Think of a car for example. The car chassis is "ground" and it is the 0volt potential reference but since it is riding on rubber tires it is not connected to earth, but the chassis is still "grounded".

 

[user 26281]

I'm thinking you are an A/C voltage guy? That's where our terminology is getting crossed. Just because the tin hull is in direct contact with the water (or earth) it does not mean it's at 0 voltage potential. The earth is not the "ground" in a D/C system like it is in an A/C system. Think of a car for example. The car chassis is "ground" and it is the 0volt potential reference but since it is riding on rubber tires it is not connected to earth, but the chassis is still "grounded".

Retired avionics engineer.

ABYC definition - The potential of the earth's surface. The boat's ground is established by a conducting connection (intentional or accidental) with the earth, including any conductive part of the wetted surface of a hull.

A tin boat is at earth ground potential when in the water.

Worked many DC systems that used earth ground.

 

[MDCrappie]

Retired avionics engineer.

ABYC definition - The potential of the earth's surface. The boat's ground is established by a conducting connection (intentional or accidental) with the earth, including any conductive part of the wetted surface of a hull.

A tin boat is at earth ground potential when in the water.

Worked many DC systems that used earth ground.

Gotcha, kinda guessed you were an engineer. I'm not, I'm more real world experienced. I base my judgements on what I have seen. I use analytical reasoning.
No reason to have an argument about the specific wording. Not going to persuade those who refuse to "ground" their hulls anyway, one way or the other.

 

[LDUBS]

Can you direct me to what you've read?

I simply googled should I ground my 12V battery to my aluminum boat hull. I did try to understand ABYC's rules but got lost in the terminology. Though they do seem to say that if the elect system is to be connected to ground, that connection is to be to the motor. Again, I may be misunderstanding this.

Can you direct me to what you've read?

With this "free floating"system what happens if one of your positive wires gets chaffed and makes contact with the aluminum"? In my boat if this happens it blows a fuse and I know there is a problem. In your boat nothing will likely happen with the electrical system at all. Now put your boat in the water and leave it there for a couple hours.
Without the fuse blowing (since the hull is not bonded to the negative) your boat hull essentially becomes the positive. Your motor is grounded so it is the negative. Once in the water current will flow and guess what becomes the sacrificial anode

Before reading your comment I would have thought if a wire shorted to the hull, it would blow the fuse.

I note in ABYC's common wiring diagram for outboards, the negative wiring is attached to three places: The battery negative terminal, the outboard, and a negative bus bar (for accessories). The outboard is shown as the "ground". It does not show a connection from the battery negative to the hull. This seems to be standard practice with every aluminum boat. So my question again is if it is better to "ground" the battery negative to the hull, why isn't it done?

Not to further muddy the water, but for those aluminum boats with built-in gaso tanks, are the tank's metal components (like the fill) normally grounded to a negative bus?

Edit: I may have pushed the button at about the same time as the previous posts. Sorry if there is overlap.

 

[user 26281]

I simply googled should I ground my 12V battery to my aluminum boat hull. I did try to understand ABYC's rules but got lost in the terminology. Though they do seem to say that if the elect system is to be connected to ground, that connection is to be to the motor. Again, I may be misunderstanding this.



Before reading your comment I would have thought if a wire shorted to the hull, it would blow the fuse.

I note in ABYC's common wiring diagram for outboards, the negative wiring is attached to three places: The battery negative terminal, the outboard, and a negative bus bar (for accessories). The outboard is shown as the "ground". It does not show a connection from the battery negative to the hull. This seems to be standard practice with every aluminum boat. So my question again is if it is better to "ground" the battery negative to the hull, why isn't it done?

Not to further muddy the water, but for those aluminum boats with built-in gaso tanks, are the tank's metal components (like the fill) normally grounded to a negative bus?

Edit: I may have pushed the button at about the same time as the previous post. Sorry if there is overlap.

If you have an ohm meter, got to your boat and ohm from hull (non painted surface) to (-) of starter battery. There is probally a 99% chance that you will have 0-5 ohms of resistance. This means that your battery is already connected to hull through the motor contact bolts/sufaces. Assuming good wiring in your boat, everything connected to (-) terminal is electrical the same point.

I have personally never seen a electric start outboard motor installed with isolation hardware that would prevent, grounding the hull through the motor.

So if your boat is like mine, and your hull is grounded through the engine, it's either designed that way or there are lots and lots of motors installed incorrectly.

Agree that ABYC always shows and recommends the engine as the ground. I don't have access to all there docs and would just be guessing. Never looked at internal tanks, so I can` t give an answer.

 

[LDUBS]

If you have an ohm meter, got to your boat and ohm from hull (non painted surface) to (-) of starter battery. There is probally a 99% chance that you will have 0-5 ohms of resistance. This means that your battery is already connected to hull through the motor contact bolts/sufaces. Assuming good wiring in your boat, everything connected to (-) terminal is electrical the same point.

I have personally never seen a electric start outboard motor installed with isolation hardware that would prevent, grounding the hull through the motor.

So if your boat is like mine, and your hull is grounded through the engine, it's either designed that way or there are lots and lots of motors installed incorrectly.

Agree that ABYC always shows and recommends the engine as the ground. I don't have access to all there docs and would just be guessing. Never looked at internal tanks, so I can` t give an answer.

Thanks. I'll drag out the ohm meter tomorrow (it is an old cheap analog model). My outboard is bolted to the transom (metal to metal). No isolation that I can see.

I learn a lot in these discussions. Unfortunately, you guys are subjected to my dumb questions. Lol.

 

[user 26281]

Thanks. I'll drag out the ohm meter tomorrow (it is an old cheap analog model). My outboard is bolted to the transom (metal to metal). No isolation that I can see.

I learn a lot in these discussions. Unfortunately, you guys are subjected to my dumb questions. Lol.

I checked mine numerous times, it's definitely connected hull to (-) through the motor.

Just for curiosity, I will check my motor install manual, to see what it states.

I will try to post a quick video, showing the ohms check.