Wiring aluminum boat

[fishNduck]

Hey everybody, new to the forum. I have an old ('88) aluminum 16ft boat im just starting to tear down and rebuild. I'll have some pics up in a little bit.

My first question-how do you ground the wiring (and generally setup the wiring system) safely to an all alum boat? I plan on having two 12V, one starter bat strictly for the engine, and a deep cycle for the trolling motor, running and a few interior lights, bilge, aerator, and fishfinder.

Thanks for any help/suggestions...ill definitely have some more questions once i get a general layout and some pics.

[redtech]

first never ground to the boat always to the battery or grounding block
uscg would say running lights and bilge go to the starting battery the rest is up to you on witch on to use.

[fishNduck]

Thanks redtech

Dumb question, but i dont know much about wiring...how do you ground, say a light to a battery? Just run the wire that is supposed to be grounded to the positive or negative terminal of the battery?

[marshmat]

Most North American vehicles of any sort, boat or car, are wired negative-ground. This just means that all devices share a common connection to the negative bus bar, which is connected to the battery negative. It's just as possible to do positive-ground (as in old British cars) but in the interests of keeping things standardized, we usually make the negative the common terminal.
You might find http://www.boatdesign.net/wiki/Electrical_systems useful.

[redtech]

fishNduck, grounds are mostly black wires in the us and a ground in dc terms is mostly just a return to the negitive poll of the battery
so yes to ground a light power just needs a return to the neg battery post to use less wire you can connect grounds is series or use a grounding block that will have one large lead to the battery and multipule leads leads coming from lights, horn, stereo, ect...
use a fuse at the battery pos to a fuse block at the helm then use the right fuse on all your electrical from there
you can't get hurt doing dc for the most part but if you don't understand it there are some good books and web sight that can help
good luck and drink beer only after the job is done cheers now

[sauserj]

Originally Posted by redtech

first never ground to the boat always to the battery or grounding block
uscg would say running lights and bilge go to the starting battery the rest is up to you on witch on to use.

Why do you never ground to the boat?

[redtech]

electrolysis and corrosion

[Frosty]

You will never ever stop the hull from being grounded (negative).

The engine block is negative it has to be for oil pressure sw ,temp sw, starter. Even if you strap the engine straight to the batt the hull is neg.

(Oh but the engine is on rubber mountings) Ok throttle cable, stop pull cables. Or even the cooling water in the sea cock.

[lazeyjack]

of course you can not isolate, in fact you must ground the hull by negative, in one place, then run two wire system to pos and insulated bus. But no matter how many times one tells this, the same old stuff comes up

[redtech]

you can never stop the hull from being grounded and you what to ground it but you still don't want to promote the hull as a ground either
for wiring the hull is not a conductor you want to use in realality there is nother you can do but limit it from being a conductor

[Frosty]

If the hull is negative, then its grounded. It should be and needs to be. Any flow of electricity is irrelevent. Anodes on an alluminium boat needs carefull considerations and I would fit an electronic detector.

[lazeyjack]

Originally Posted by redtech

you can never stop the hull from being grounded and you what to ground it but you still don't want to promote the hull as a ground either
for wiring the hull is not a conductor you want to use in realality there is nother you can do but limit it from being a conductor

before you give this misleading info, I would ask how many yachts have you wired or built?
well i built and wired 32 from go to whoa, and I can tell you that all superyachts ground their batts, and also people like hamilton jet do not guarantee there very expensive (like over 100k jets) without the hull being grounded to the neg batt terminal
normally I would not post this, but this is the 4th time you have posted the incorrect stuff, frosty is dead right too
www.alloyyachts.co.nz
you think these people would risk a 100mill yacht?

[thudpucker]

You dont want to use your aluminum boat for a ground wire. There are some weird things that will happen if you do.
Especially if you have one of those Riveted boats (starcraft)

However I have grounded my Bow light to the boat on my little 12' skiff and its never been the cause of a problem.

But if you have a big complex boat and lots of gear, just run black wires from the Ground Buss to everything. It's only another 50' of wire, a few bucks, and once its done properly you wont have any more problems.
Only one Black wire from the Negative terminal of the Battery to the Ground buss. Make it a clean neat looking job.

Plan your schemetic so you have only one Red wire
wire from the Battery to a Buss.
The positive wires all eminate from that Buss.
Use fuses.
Make them easily accessible when your out on the water and have places for spare fuses right at the Positive buss.

Get your stuff from a good Marine boat supply store.

[marshmat]

I'm not a marine electrician so don't take my word as law. But to summarize what's been said and what is typically done on metal boats I've seen:
- Positive electrical connection to each device should be by appropriately sized copper wire, colour coded by function/system (there IS a standard colour code to be used for boats, that is not the same as a house or car's colour coding).
- Negative connection to each device should be by appropriately sized copper wire to a common negative bus bar, which is connected to the battery negative.
- Conductive components of the boat and its hardware are bonded by copper wire to each other and to the battery negative. (Those of you who are familiar with electrical engineering principles will recognize that this bonding forces all of these metal components to be at the same potential, thus there can be no potential difference between metal components which could lead to galvanic corrosion problems. An unbonded, powered component will have a potential difference between it and the hull, roughly equal to the voltage loss in its negative cable between it and the battery.)
I'd add to thudpucker's comment that if you're going to use fuses, the rectangular plastic ones used in cars are a heck of a lot more durable than the glass tube ones used for stereos etc.

[Ike]

Whoa guys we are getting way confused here over ground and groundING. There is a difference. I will asume for the moment we are talking just dc.

The ground wire in a DC system is the negative wire, generally black (yelllow in Europe). The red wire is the positive side. Look up the colors codes to find out what color your postive wires should be to different pieces of equipment. http://newboatbuilders.com/pages/elect5.html

DC systems are two wire systems and although the red is consider the hot side, actually both sides conduct current. It just goes around in a big circle through the red out to the light or whatever, and back to the battery through the black. ABYC standards and ISO and a bunch of other standards, all say the same thing. DON'T USE THE HULL OF A METAL BOAT AS A CONDUCTOR. So you will have a positive wire and a negative wire connected to all your DC electrical equipment.

The negative side is ground, and this is connected from the battery or from a ground bus (a board with a lot of terminals on it that have a common wire that goes to the negative post on the battery) to the engine block. The engine block is the common ground point.

So what is a groundING wire? That is the GREEN wire. Yes, DC systems can have a green wire. The green wire is used for two things. One is in case you have a ground fault (an accidental short to ground), the other is for what is commonly called bonding. Bonding is hooking all the metal fittings, metal cases of appliances, etc to the common ground, AND this can include the hull of the boat. ABYC and others allow this because NORMALLY this wire never carries any current.

Over on the AC side we have a three wire system as well. It also has a green wire (sometimes green with a yellow stripe). That same green wire is connected to the common ground, the engine block and thus to the green wire for the DC system.

However, as has been rather strongly pointed out the hull is never used as a conductor. This is due to the galvanic corrosion problem, and if you have a AC system with a green wire connected to the common ground, and get a short to ground, now the hull is suddenly conducting 120V ac! And you get AC leakage current into you DC system as well.

So Do Not use the hull as a ground. It can be connect to the groundING system for protection from galvanic corrosion and stray currents. But not as a conductor.