wiring alloy boat system

Steel and aluminum boatbuilding. See: "Boatbuilding Methods", in left-hand column of the Home page, for information about alloys.

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carlos bairo
Posts: 85
Joined: Mon Mar 31, 2008 10:12 pm
Location: SYDNEY AUSTRALIA

wiring alloy boat system

Post by carlos bairo » Thu Nov 15, 2012 12:19 am

hi i have build the CARIOCA 18'6''on aluminium,at this stage i work on electrical system for a single outboard engine,
with tow battery ., i ll like to ask for a schematic distribuition system ,i m a bit confuse of the diferents oppinions on the
appropiate installation on aluminium boats, any healp welcome
cheers
CARLOS
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Trackhappy
Posts: 1412
Joined: Wed Feb 17, 2010 5:42 pm
Location: Sunshine Coast, Queensland, Australia. Building Gentry.

Re: wiring alloy boat system

Post by Trackhappy » Thu Nov 15, 2012 2:00 pm

Hi Carlos.

I'll see what I can find around as far as a diagram, but there is one basic rule for a metal boat, and that is isolate everything from the hull (positive AND negative). Don't treat it like a car where you run positive wires and get the negative off the nearest metal. This helps keep any stray currents from causing electrolysis and eating away the boat and is known as "floating"
For the rest of it, with an outboard a lot of the work is done for you as they tend to come with their own wiring harnesses. If you are adding a second battery, just leave the outboard/starting battery system alone and buy a good dual battery unit which monitors the start battery and starts to charge the second battery only when the starting battery is fully charged (or just when the engine is running on cheaper versions).
From the second battery, run negative to a bus bar and split out from there to the required parts of the boat. Run the positive to an isolating switch then to a large (30 amp) fuse, to the bus bar and off to a circuit breaker/switch panel for your accessories. At that point it depends upon the details of the boat as to how you wire it. Use heavy gauge wire to up to the breaker panel then smaller wires off to the various accessories. Place the breaker panel close to the majority of the accessories so as to avoid running lots of little cables around.
Buy specific marine wire which is tinned (coated with solder) before being covered as this helps prevent corrosion. Keep everything as short as possible to avoid loss in the wires, keep it all neat and accessible. Watch for possible future physical damage due to movement, pinching, and of course water. Solder connections and use heat shrink. Think ahead about possible future extra's as it is always messy to add later. Use vaseline or silicon on exposed connections such as the battery terminals/isolating switch. If you want to form a loom, use self amalgating tape, which is a form of self vulcanising rubber used on external electrical joints and completely wrap it. Plastic tape tends to unstick over time, I personally don't like it much.


Hope that helps.
Glenn.
By the time I have built a boat, I'll be ready to build a boat....

Kevin Morin
Posts: 699
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: wiring alloy boat system

Post by Kevin Morin » Mon Apr 01, 2013 10:10 pm

Carlos, Track

One thing not mentioned here (yet) is the the battery bond. The Negative of the Battery should be bonded to the metal hull with a large copper conductor so there is no electrolytic potential from the battery power system to the hull.

This is not to address galvanic corrosion (zincs) but to avoid an electrolytic cell between the DC or AC system and the hull; electrolysis.

All metal boats with an engine charging system for a battery powered electrical systems should have a bond from the battery Neg to the hull. This is not a "ground".

Cheers,
Kevin Morin
Kevin Morin

Trackhappy
Posts: 1412
Joined: Wed Feb 17, 2010 5:42 pm
Location: Sunshine Coast, Queensland, Australia. Building Gentry.

Re: wiring alloy boat system

Post by Trackhappy » Tue Apr 02, 2013 2:33 am

Good point Kevin.
The key here is this is bonded AT ONE POINT ONLY!. This is very important. Personally, I'd use an alumnium lug crimped onto the copper conductor so if there were any galvanic or electrolytic action it'll be between the lug and copper conductor not the lug and some part of the boat. Also make sure this point is sell above the water level in the boat as the liquid acts as the electrolyte which enables the reaction.
This bond also allows the boat hull to act as a ground plane for the radio antenna.
By the time I have built a boat, I'll be ready to build a boat....

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