Moderated Discussion Areas
ContinuousWave: Small Boat Electrical
|Author||Topic: Basic Wiring|
posted 03-07-2008 07:41 AM ET (US)
To begin with I'm an electrical idiot. I bought one of the strip waterproof LED lights I would like to install in the console of my MONTAUK 170. I would like to wire it to the accessory switch, how do I do that? Thanks
posted 03-07-2008 08:50 AM ET (US)
To control an electrical load with a switch, wire the switch in series with the current supply to the load. Usually in 12-volt DC wiring on a boat the negative battery terminal is the common. Any disconnect should be made in the positive lead.
posted 03-07-2008 09:18 AM ET (US)
So the negative wire should go to the battery or the negative side of my on/off switch and the positive should go to the positive side of the switch?
posted 03-07-2008 11:43 AM ET (US)
It is often seen that in a 12-volt distribution in a small boat there is a battery negative bus provided which has sufficient unused terminals to permit the addition of several owner-added electrical devices.
It is good electrical wiring practice to only have one terminal under each screw, however, this rule is not always observed in practice. If you have to put two ring terminal connectors under one screw you won't be doing too much harm.
In a Boston Whaler it is typical that there are pre-wired switches for accessory loads. You can connect the load to the switch.
posted 03-07-2008 12:08 PM ET (US)
Thanks again Jim
posted 03-08-2008 10:10 AM ET (US)
Boston Whaler has kindly provided us with the wiring diagram of their 2007 170 MONTAUK on-line at
Please refer to that diagram. You will see that there is an existing switch on the helm console for control of owner-added accessories. You connect the accessory load positive lead to terminal 3 of the ACCESSORY switch. You connect the accessory load negative lead to the bus marked MAIN GROUND BUS. There should be a spare terminal on the bus. The circuit is fused for a maximum current of three amperes.
posted 03-08-2008 10:18 AM ET (US)
Follow the recommended color code practice for wiring as detailed in
and use the existing wiring as a guide for how to route and dress the wiring you install. Use appropriate wire. The wire should be multi-stranded, tinned, and have vinyl insulation rated for marine use. Use a sufficient length of wire and avoid stretching the wire taunt.
Use some plastic wire fasteners (Ty-Wrap's) to fasten the new wire to existing wire bundles.
Use appropriate connectors, with ring terminal or push-on arrangements, to connect the new wiring to the existing switch and bus terminals. You can likely find the appropriate wiring devices at a marine supply or even at a hardware store electrical department.
posted 03-08-2008 12:55 PM ET (US)
Here is a good reference for boat wiring.
posted 03-08-2008 09:53 PM ET (US)
Seahorse: Page 3 of your reference sez:
"Boats powered with outboard engine(s) are not subject to
Net: those regs don't apply to most of our boats.
However: They do provide a pretty good set of guidelines for
posted 03-09-2008 12:07 AM ET (US)
Feejer, Jimh and others are giving good information, but your response to Jimh's first post made me think that we may not have given you that basic info you need. The light needs to have its positive lead connected to the positive side of the battery and its negative lead connected to the negative post in order to light. In order to turn the light on and off you cut the positive lead and wire the two cut ends to a switch. In practice you may be able to find an unswitched source of +12 volts and ground (negative) closer to your new light and switch. This will usually look like a strip of plastic with a metal bar and a bunch of screws. One large wire will be connected to the battery or fuse, and a bunch of smaller wires will snake off to the various electrical devices. If there are any leftover screws, use those. If not, you could twist your new wire with an existing wire and tighten the screw down on them. They should wrap around the screw in a clockwise direction. If you do go all the way back to the battery with new wire, buy an inline fuse and put it near the battery on the positive side. Good luck, and consider having a friend work with you. Even if he or she does not know more than you do, the process of discussing and explaining your plan will help to catch mistakes and give you confidence. Dave
posted 03-09-2008 09:54 AM ET (US)
As mentioned already, it is not a good wiring practice to make multiple connections to a single wiring post, and no where is this advice more important to observe than at the battery terminal posts. Installations in which there are multiple wires run to the battery posts and many connectors are held in place under one terminal screw are not good practice.
About the only case which one might allow in which there could be two wires connected to a battery positive terminal post is for a separate "keep-alive" feed to a bilge pump which is to remain powered even with the primary battery distribution switch is in the OFF position. But accumulating a lot of individually run and individually fused conductors for connection at the battery positive terminal is not recommended.
You should never connect a wire to a terminal without using a ring terminal connector. Bare wires should never be wrapped around screws and tightened. That is simply not acceptable wiring practice, and it should be avoided in all but emergency situations.
posted 03-09-2008 09:58 AM ET (US)
This discussion demonstrates a principle which I have long held: it is difficult to explain the art of proper electrical wiring practice in a narrative form. My recommendation to readers who are not familiar with the art of proper electrical wiring, with electrical devices in general, and with 12-volt marine electrical systems in particular is to seek a well-written and well-illustrated book on this topic and learn from it.
posted 03-10-2008 07:41 PM ET (US)
Any examples of good, easy to understand books?
posted 04-06-2008 12:26 AM ET (US)
Feejer, were you able to figure out how to hook the positive wire to the accessory switch? I have a 2007 Montauk 170 and I would like to do something similar. I have studied the wiring diagram and spent a fair bit of time with my head in the console trying to figure out where the positive (red) wire attaches other that to the battery and I am no wiser now that I was before. I know I can hook the negative (black) wire to the ground bus but I can not figure out how to connect the positive wire to the accessory switch.
Any advice you can send my way will be greatly appreciated.
posted 04-06-2008 05:24 AM ET (US)
Heres a good simple reference for those of us who aren't electricians. Its called Basic Auto Electricity. [I know, but all the principals are the same.] Its by StreetWorks Rod & Custom P.O. Box 270, Bozrah, Ct 06334. Ph. 860-859-0513. Cost was $6.95 a while back. Only has 48 pages, but it covers all the 12V DC stuff. Aloha
posted 04-06-2008 10:36 PM ET (US)
While the principles are the same between auto and boat
electricity, the hardware is different. Marine grade stuff
is built to survive in the damp, vibrating, bouncing, marine
Nigel Calder has a good book on boat electricals, and there's
|Casco Bay Outrage||
posted 04-06-2008 11:18 PM ET (US)
Email me offline (n my profile) and I can walk you through it via the phone and an email or two.
C B O
posted 04-07-2008 09:51 AM ET (US)
Thanks guys for all the info. The boat is still in storage (until April 14th). I plan to do the [lamps] sometime in April or May. I'll post some pics when I have them installed
posted 04-08-2008 11:10 PM ET (US)
Where did you buy the [lamp]?
posted 04-09-2008 10:46 AM ET (US)
Take your LED light to your car battery and make sure you find out which wire is negative (usually black). LED lights only work in one direction unlike incandescent bulbs.
I ran the negative wires to the negative block. My switch receives it's power from a circut breaker under it, I ran the positive to the switch.
posted 04-09-2008 12:33 PM ET (US)
This is what and from where I bought
LED Light Strip 25 Ultra-Bright White DC Instrument
posted 04-09-2008 06:35 PM ET (US)
Liteamorn: a lot of LED lights have a diode system so it
doesn't matter how you hook them up. Those that don't, the
negative wire will be black.
But it's worth checking it out on your car battery (or the
posted 04-11-2008 09:42 AM ET (US)
My lights are actually for a different vehicle (can't go into detail)the black wire is not the negative, the white one is. My red lights have a black wire but it is a positive lead.
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