How to wire a boat?

Question

I need to Wire a boat from scratch and am not sure how. I will need to run the lights, electric to start the outboard engine, and the gauges and whatever else I need to get goin. Any help would be great!!

Answer 1

All the answers (so far) have good nuggets of info.  The most important one is : if you don't know what you're doing, or even if you are a little unsure, GET HELP!  Direct current electrical wiring is not difficult, but you must pay attention; a seemingly small mistake can set your boat on fire, and it will happen when you are out on the water (don't sneer at Murphy's Law).

Fuses are a must.  DON'T skip them; a blown fuse WILL save your boat from a fire.  Fuses that blow frequently in a properly designed system do so for one of two reasons: the circuit is overloaded (too many loads or an oversized load), or the circuit is shorting out (damaged wire, damaged load, etc).  NEVER assume the fuse is too small for the circuit; the purpose of the fuse is to protect the WIRE, NOT the LOAD!  Select the wire gauge according to the needs of the circuit, and choose the fuse accordingly.  If you aren't sure exactly how much current you need on a given circuit, get a good ballpark estimate (based on actual research; don't guess), and go a size larger.  Go a size larger if you are running a length longer than ~15 feet, or if the wire will be in a conduit that will not allow good heat dissipation.

This is important enough to repeat: don't skip the fuses, fuse each circuit according to the wire size, and don't change the fuse size for any reason.  

Bus bars are very handy for circuit distribution and help avoid having to pull 20+ foot continuous runs.  They also make troubleshooting much easier by giving you a easy test point.

If you don't have a circuit diagram of the original wiring, you should do some research and draw up one of your own.  This will give you a plan to work from.  If the original wiring is still in the boat, you can use it to develop the diagram.

Here are some quick numbers:

Max amps ------- wire gauge

5 amps  ----------- 18 AWG

10 amps ----------- 16 AWG

15 amps ----------- 14 AWG

20 amps ----------- 12 AWG

30 amps ----------- 10 AWG

These are the same gauges used in house wiring.  DON'T use the solid house wiring in boats; you MUST use stranded, as the natural flexing capability of the wire is necessary to prevent cracks.  It must be copper (NOT aluminum or AL/CU) for the same reason.  Aluminum also has more resistance and will heat up more at the same load.  I believe there are marine versions of the copper stranded (low corrosion?).  Use solder-less connectors (crimp-on); soldered wires are like solid wires: prone to cracking, and the different metals can act like a bettery and corrode very quickly.

I've done well more than my share of wiring (house, car, boat, robots,etc).  Take your time, pay attention to detail, run a separate ground wire for every circuit (no "frame" grounds on a boat), and don't hesitate to get a good reference book (or three), if for no other reason than to do a sanity check.

Answer 2

Get a wiring diagram for the type of boat and motor you have and start to wire. If you dont know basic electrical circuits i would suggest you learn them first or you will have nothing but grief!! Not to mention a fire!!

Answer 3

the easy way is to break it down to smaller blocks and trouble shoot it as you go along. when we did my buddys boat last year we did the lights first then the audio, starter then motor then we added the gauges just remember the grounds should be tied together and the gas tank also.

Answer 4

I would recommend that you use bus bars. You can run your hot and ground to two separate bus bars under the console, then each system on your boat can be run from the bus bars. You will need to ensure you use heavy enough wire on your buses to handle the amount of amps each circuit uses. Also, put fuses on each circuit to protect your equipment such as stereo, fish finder, lights, blowers, bilge pumps......etc.  The wiring for the outboard will be encased in the harness provided with the engine. These are usually color coded and easy to install. There should be instructions on how to wire the ignition switch with the harness. You will also have a battery wiring harness coming off the engine that go directly to the battery.....hot and ground.    Good luck.