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Thread: Wiring the boat

  1. #1
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    Default Wiring the boat

    Another big job coming up with my Ninigret build is wiring the boat.
    I have been studying The 12 Volt Bible for Boats, and The 12 Volt Doctor's Practical Handbook.
    Pretty steep learning curve, but I'll get it...
    I can hook up something and make it work... but wire sizing, fuse sizing, total amperage on a circuit, voltage drops, etc. I have mostly never given much thought to...
    Of course I want this thing done right, and safely, so at this point I am getting all this 12 volt elec-trickery ingrained in my brain.
    Another adventure in building boats.
    I love learning new stuff...and putting it to work.

    So far they are both good books...so if you are in the same boat as me you might wish to try them.

  2. #2
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    Default Re: Wiring the boat

    An adventure for sure! Check out Nigel Calder's Boatowner's Mechanical & Electrical Manual. He knows his stuff.

    Make sure to use tinned marine wire & quality crimp connectors. Non-tinned will corrode & cheap connectors don't last. If using a battery charger or inverter/charger hooked to shore power, make sure to install a galvanic isolator. If using an inverter, all 120 outlets need to be GFI protected just like in a bathroom or kitchen.
    "If it ain't broke, you're not trying." - Red Green

  3. #3
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    Default

    Stick to the ABYC color code. It will make trouble shooting down the line easier.




    Kevin


    Sent from my iPhone using Tapatalk Pro
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  4. #4
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    Default Re: Wiring the boat

    Hi,

    I think the most import concept to remember is that the over current protection (breakers / fuses) are in place to protect the wires. They need to be sized accordingly to not allow enough current to flow in the conductor to turn it into a toaster element.

    Cheers,
    Mark

  5. #5
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    Default Re: Wiring the boat

    All the above, plus, keep the wiring accessible! Put it behind mouldings or coverings which can be easily removed.

    Most boats end up being a rat's-nest of wires after a while...

  6. #6
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    Default Re: Wiring the boat

    As said above, get a copy of Nigel Calder's book. Also the marine electrical component companies such as Blue Seas have lots of info and data (on wire sizing, etc) on their websites. DC wiring isn't hard, just follow the rules.

  7. #7
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    Default Re: Wiring the boat

    You can buy, already made wiring harnesses made for boats.
    Denise, Bristol PA, retired from HVAC business, & boat restoration and building

  8. #8
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    Default Re: Wiring the boat

    ABYC Wire Sizer App

    https://abycinc.org/page/wiresizer#:...20requirements.

    I haven't done much more than play around with it, but from what I can tell, its gives good answers as to wire size. Which if you get it right, is 90% of the battle.

  9. #9
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    Default Re: Wiring the boat

    I am still at the beginning stages of learning and understanding this stuff.....
    One thing that I have found out that kind of floors me is the huge amperage difference between wiring things in parallel or in series.
    Still trying to grasp that whole thing.

  10. #10
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    Default Re: Wiring the boat

    I cannot think of one single circuit that needs to be wired in series Tim. Anybody else?

  11. #11
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    Default Re: Wiring the boat

    My Honda 20 comes with about 7 feet or so of #6 battery cable so I ran #4 with the red (positive) thru a 100A fuse then thru a battery switch to a set of bus bars, one pos. with a protective cover and one neg., where I connected the outboard, the pot hauler with #6 as recommended by the manufacturer and everything else with #14. The 100A fuse is pretty big but it's what the hauler needs. One of the wires in the wiring bundle from the outboard is hot when the ignition is on so I connected that to the volt meter and compass lite.

    Correction...Fuel gauge and compass lite.
    Last edited by Gib Etheridge; 03-29-2021 at 11:31 PM.

  12. #12
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    Default Re: Wiring the boat

    Quote Originally Posted by Gib Etheridge View Post
    I cannot think of one single circuit that needs to be wired in series Tim. Anybody else?
    Series? Absolutely not.
    "If it ain't broke, you're not trying." - Red Green

  13. #13
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    Default Re: Wiring the boat

    Switch and the rest of the circuit, circuit breakers and the circuit that it is protecting.

  14. #14
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    Quote Originally Posted by Gib Etheridge View Post
    I cannot think of one single circuit that needs to be wired in series Tim. Anybody else?


    Wire in series you get 24v.
    Because of Ohm: double the voltage you HALVE the amperage. This allows use of lighter, less expensive cable and wiring. This is common on boats @ 35 ft plus LOA

    Aboard a small boat, you might have a 24v circuit for a high draw appliance, like a trolling motor, a bow or stern thruster or a gyro stabilizer. That's about it.

    Kevin


    Sent from my iPhone using Tapatalk Pro
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  15. #15
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    Default Re: Wiring the boat

    Get Calder's boatowners mechanical and electrical. It's the bible for this sort of thing. I'm about a third through it. It's more like a university text book than a novel and reading it is similar to reading a physics text or something. But It's got all the info you'll be looking for in it. Also have a look at Pacific Yacht Systems (link below). They also have a youtube Channel. The owner of PYS puts up informative, educational videos, copies of lectures he's given at boat shows etc. There's an absolute treasure trove of information.

    Pacific Yacht Systems: Marine Electronics And Electrical Systems, Marine Boats Vancouver, Sailboats Vancouver, Boats Electronics (pysystems.ca)
    If one advances confidently in the direction of his dreams, and endeavors to live the life which he has imagined, he will meet with a success unexpected in common hours.
    -Henry David Thoreau-

  16. #16
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    Default Re: Wiring the boat

    Heute ist so ein schöne Tag...

  17. #17
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    Default Re: Wiring the boat

    I liked Charlie Wing’s book as linked above. / Jim

  18. #18
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    Default Re: Wiring the boat

    We had a boat with a house bank of four 6V golf cart batteries. So two pair in series, the pairs connected in parallel. Getting all four batteries to charge evenly was a struggle. I wouldn't recommend it.
    -Dave

  19. #19
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    Default Re: Wiring the boat

    Quote Originally Posted by Woxbox View Post
    We had a boat with a house bank of four 6V golf cart batteries. So two pair in series, the pairs connected in parallel. Getting all four batteries to charge evenly was a struggle. I wouldn't recommend it.
    The trick is having exactly the same length cables - which often means having some extra coiled alongside one or 2. Or you can use a buss. In my off grid house I had 2 layers of 6 volt batteries. Each layer was in series for 24 volts & connected to copper bars, with the connection going to the inverter in the middle. When adding water every couple of months to the 8 batteries they were within a tablespoon of each other.
    "If it ain't broke, you're not trying." - Red Green

  20. #20
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    Default Re: Wiring the boat

    Other than for a starting harness and bilge pump I'd go with wireless/rechargeable/solar stuff now for nav lights and night lighting. Items can be taken ashore, checked and kept dry between trips. Less drilling of holes and running wires.
    “Eventually, all things merge into one, and a river runs through it. The river was cut by the world's great flood and runs over rocks from the basement of time. On some of those rocks are timeless raindrops. Under the rocks are the words, and some of the words are theirs."

  21. #21
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    Default Re: Wiring the boat

    Quote Originally Posted by Gib Etheridge View Post
    My Honda 20 comes with about 7 feet or so of #6 battery cable so I ran #4 with the red (positive) thru a 100A fuse then thru a battery switch to a set of bus bars, one pos. with a protective cover and one neg., where I connected the outboard, the pot hauler with #6 as recommended by the manufacturer and everything else with #14. The 100A fuse is pretty big but it's what the hauler needs. One of the wires in the wiring bundle from the outboard is hot when the ignition is on so I connected that to the volt meter and compass lite.

    Correction......Fuel gauge and compass lite.
    Sorry.

  22. #22
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    Default Re: Wiring the boat

    Don Casey's book is very well written and easy to understand. It's more geared to the practical side of the installation. Highly recommend it!

    Have Calder's book too and it's a wealth of information but is mostly written for the cruising sailboat owner with a more complicated electrical system.
    Attached Images Attached Images
    Last edited by Woody Jones; 03-30-2021 at 06:34 PM.

  23. #23
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    Default Re: Wiring the boat

    I could be wrong but I went through this on my universal diesel rewire, it had an amp meter but I believe the shunt for an amp meter runs in series with the load. It wasn't difficult to make a new wiring harness and install an volt meter where the amp meter was
    Denise, Bristol PA, retired from HVAC business, & boat restoration and building

  24. #24
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    Default Re: Wiring the boat

    I second Calder, great to help understand the theory if you want to dig deep. If you are serious about getting your head around boat systems he gives seminars.

    https://marinehowto.com - Great sites for the nuts and bolts - opinionated, but good practical advice but again mostly for the cruising enthusiast.

    "The 12 Volt Doctor" should be all you need, a little dated but simple and straightforward and starts you out gently.

  25. #25
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    Default Re: Wiring the boat

    There is also a lot of info on small boat wiring on moyermarineforum.com (no affiliation) stuff there on the Universal Atomic 4 engine, and small boat wiring as well.

  26. #26
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    Default Re: Wiring the boat

    Last year I mostly rewired Holiday, trying to follow Calder and ABYC. I cheaped out by using automotive circuit breakers and lit switches for lighting circuits (couldn't find the right items in marine grade, and I confined these to one easily accessible panel under a cockpit seat).

    But the standards call for a minimum wire size of 16 gauge, (10 amps), which seems way oversized for LED's drawing at most 1 amp. This wire was particularly cumbersome running up the masts to nav and utility lights, and connections at the spreaders are pretty ugly! Doing it again, I think I would track down some cable - perhaps aviation-grade? - sized for the loads (protected by appropriate breakers or fuses, of course).

    Any thoughts on using smaller wire, and some auto components? This is a private vessel, insured only for liability.

    By the way, I ran wires in either the ugly black split conduit, or in prettier plastic "wiremold" which provides complete access. Photos to follow.

  27. #27
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    Default Re: Wiring the boat

    When it comes to sizing wire, it's not only the load (amps), but the distance. While the minimum circuit they list is 5 amps, the size of wire needed grows quickly as the length increases. While one could argue that an LED masthead light needs less than 1 amp - it may be that either they want 5 amps minimum or possibly that they have not updated to allow for LED's low amperage. A conventional masthead light would draw a couple of amps - so you'd want a 5 amp circuit. Also - in looking for ABYC approved circuit breakers - the lowest i found in a quick search is 5 amp.

    A chart (scroll down a bit): https://www.boatus.com/expert-advice...rect-wire-size

    A 5 amp circuit allows/requires 18 ga. for 10 ft. 16 ga. for 15 ft, 14 for 20, 12 for 30 ft.

    Ha! It let me copy the chart:

    Last edited by Garret; 04-01-2021 at 07:46 AM.
    "If it ain't broke, you're not trying." - Red Green

  28. #28
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    Default Re: Wiring the boat

    Quote Originally Posted by Garret View Post
    When it comes to sizing wire.... a quick search....
    ...
    A 5 amp circuit allows/requires 18 ga. for 10 ft. 16 ga. for 15 ft, 14 for 20, 12 for 30...
    Wow - that indicates some massive wiring for a minuscule masthead light! 6 gauge on my 34’ mast plus 16’ from the battery.

    but that is for a 5 amp draw, with max 3% voltage drop (as in sensitive electronics - last time I checked some LED’s, they worked fine down to 9V, a 25% drop). For non-critical applications, ABYC says use a 10% voltage drop.

    I found this calculator:
    https://www.calculator.net/voltage-d...ctype=standard

    suggesting that 18ga 1A is ok to 100 feet, 20ga to 60 feet. Just fuse the circuit a bit smaller than the safe capacity of the wire, as I recall length doesn’t matter in that calculation.

  29. #29
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    Default Re: Wiring the boat

    I agree - but what ABYC requires & what works are probably 2 different things.
    "If it ain't broke, you're not trying." - Red Green

  30. #30
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    Default Re: Wiring the boat

    Woody is correct, Don Casey's book is so easy to understand. I keep it on hand always. you can wire anything with it. Nigel's book is great ... but it's a lot to understand. If you have a ton of systems on board it's nice. I wired a 30 foot sailboat with all the basics no problem with Don's book. Dave

  31. #31
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    Default Re: Wiring the boat

    Just two more cents and an FYI regarding that 3-percent drop chart Garrett posted.

    It is generally accepted that because of corrosion in the marine environment, plus less than perfect connections, plus vibration aboard a boat, voltage drop is never starting from zero aboard a boat. There's always some. So three percent is a target, because, aboard boats, there is some small percentage built-in that we are assumed to be starting with once the boat goes into service, even with the most fastidious installations.

    That's not to say that bigger is always better; but that adhering to the three-percent criteria is probably a better idea.

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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