Category Archives: Boat Lighting

Nitro Nuisance

Boat Wiring Guys,

I need your help with a 1997 Nitro 640 LX fishing boat that I just purchased.

Nitro 640LX

When I put the red/green navigation light into the plug in base at the bow, it doesn't come on, but causes one of my gauge lights to light up and stay on.

Any thoughts on where this might be going wrong?



The ground wire for the dash panel area is no longer connected. Because of this, the dash is grounding through the filament in the red/green light.

Run a test ground wire from the battery negative to any ground at the helm (maybe a gauge) to confirm.

Hope this helps



Thanks for the quick response,

You were right about the ground wire. We found and fixed that, but we have another problem now.

There is a large wire with a plug that goes into the motor that there is apparently a short in.....when we turn the ignition on, it will not do anything sometimes until you move that large wire around.

What is that wire called that plugs into the motor and apparently goes to the switch as well?

We need to figure out what to get to replace it.

Thank you,


It sounds like it is your main engine harness plug.

Most of those are modular and can be taken apart. This means that you may be able to just replace some terminals instead of replacing the harness.


Manitou Pontoon Boat Wiring


I am working on a 2005 22" Manitou Osprey Pro. Is there any source for obtaining a boat wiring diagram for this pontoon?

I just recently purchased this and have been trying to fix some electrical issues. Some are relatively straightforward.

Manitou Pontoon Boat

The pontoon's stereo speaker color codes matched the vendors color codes directly, but the stereo's power hookup did not - both yellow and red leads from the stereo were tied to a the pontoon's solid red wire. There was also a red wire with a yellow tracer in the same (stereo) wiring bundle of the pontoon but it was just clipped. Is one of the these a direct battery connection and the other one an on/accessory connection? The stereo wiring diagram shows two positive connections one labeled battery and the other labeled ignition - I don't want the stereo on all the time. The sun has faded all the indications of position for the ignition switch and all the switch/breaker functions. I don't even know if the ignition switch has an accessory function/position.

I don't know if the 5 function switch panel is a standard wiring. Is there a standard layout for the switches? Since the stereo speakers and power seem to follow the standard color codes for front -rear and power, is it safe to assume all the lights, horn and other accessories follow some standard of wiring? If so what are those standards and where can I find a standard schematic or wiring diagram for those standards?

I can't wait to get out fishing on this pontoon - it has an installation for a trolling motor battery in the console with direct wiring to an outlet mounted at the bow for the trolling motor (no battery installed yet) - there doesn't seem like a way to charge this battery from the engine's alternator/charger. Is there a way to connect this battery to the the engine's alternator but not allow the trolling motor battery to try to start the main engine? I don't what to run the higher gauge wiring for that. I just want to use the trolling motor battery for the trolling motor and accessories when the main engine is not running if that is possible.

I would like to develop a wiring diagram for this pontoon but I would hate to have to start from scratch and trace out the circuits by trail and error.

Any help would be really appreciated.


It sounds like a previous owner was doing some wiring modifications. We know the Manitou crew very well, and it is not like them to have hidden wires clipped off in their harnesses.

The key switch accessory position question is based on the brand of the engine on your boat. The easiest way to tell is to turn the key switch. It will either have 3 positions (OFF-ON-START) or 4 position (ACC-OFF-ON-START). If the key has an accessory position, it will have an A or ACC on a tab on back of the key.

There is not a standard layout for the switches on your helm. I would consider calling Manitou in Lansing MI to see if they have replacement panels for your boat that would have the proper labeling for the panels.

Here is the common boat wiring color code used by most OEM boat builders, including Manitou. You should be able to use this to trace down any wires on the boat.

If you want to charge the trolling motor battery while the engine is running, you will need to run some larger wires between the starting battery and the trolling motor battery. This wire size is based on the size of the alternator on your engine. Most VSR smart battery switch systems are capable of handling 125+ amps but the limit is the size of your alternator. If you alternator is less than 20 amp, the VSR is almost a waste of money. You will need to run your outboard at full alternator output for nearly 3 hours to replace what the trolling motor can draw in less than 1 hour.

Hope this helps,


Light Switched


My boat’s navigation light switch is spliced into the negative wire.

Is this acceptable or should the switch be rewired into the positive wire. The positive wire is fused with a 2 amp fuse. Bow light

Your help will be greatly appreciated.



Although it is not a common practice, there is nothing really wrong with switching the negative lead instead of the positive lead.

The best practice is: source of power, circuit protection within 7 inches of power supply, switch, device, ground.

Hope this helps,


Nitro Navigation

I have a 2010 Nitro Z7. When I tried to use the navigation lights for the first time they wouldn’t work.

I checked the fuses. The fuse box isn’t marked as to which fuse is for the lights, so I had check them all. The last fuse, a 5 amp, was blown. So I plugged another 5 amp fuse in and it immediately blew.

What is my problem?Nitro bass fishing boat

Please help


Hi Dean,

There is a short in the circuit that is causing the fuse to blow.

Trace the wire leaving the fuse panel. It should go from the fuse, to the switch, and to the device.

If the switch is not turned on, but the fuse still blows, the problem is between the switch and the fuse. If the fuse only blows when the switch is turned on, then the problem is between the switch and the device.

Hope this helps,

Reset Revival

Hi Kevin,

I screwed up my boat wiring and hope that you can help.

I have a 2004 Sylvan 18 I/O. I had to jump it the other day and in my hurry I hooked up the boat battery cables in reverse. Push to reset breaker

I have power to the bilge pump, boat horn and navigation lights, but the other side of the dash has no power at all. This includes starter switch, bilge blower, and radio. I checked the fuses but found none bad.

Did I miss a fuse down on the starter?



Hi Maurice,

There is a push-to-reset circuit breaker on the engine that supplies power to the dash. It should be a red button about 3/8″ diameter on the stbd side of the engine near where the main engine harness plugs in.

Hope this helps,


Backward Boat Wiring?

Hello Kevin,

I am trying to replace the white all-round navigation light on my fishing boat wiring.

My old light had two wires, blue and black which were connected to a black and gray on my boat. My new Attwood light has three wires. One black and 2 red labeled rear and aft. Attwood LED all round white navigation light

How do I wire this?



Hi Tom,

Connect the black to the black and both reds to the blue.

Hope this helps,



I appreciate your quick response, but I tried that and it didn’t come on.


Hi Tom,

Is the new light one of the Attwood LED navigation lights?




No, the package doesn’t designate it as led. It’s titled as “Anchor/Stern Light Combination.”


Hi Tom,

It may be polarity sensitive and your boat may be wired backwards.

Either check the black and blue on your boat with a meter or try hooking up the black on the light to the blue on the boat and the reds on the light to the black on the boat.


Boat Wiring Size


Thank you for your answers to so many electrical questions. I plan to redo my fishing boat wiring and have a couple of questions.

My 1977 18 foot Starcraft has an outboard motor with it’s own circuit and will not be involved in the rewire.

My current marine electrical has a battery in the back of the boat, approximately 16 feet from the fused, marine electrical switch panel.Click to download Kevin's boat wiring size calculator

The old boat wiring is a rat’s nest with each circuit wired individually.

I will be using the standard small boat items: a depth finder, FM radio, bilge pump, navigation lights (bow and stern), gauges and a rear-mounted gas tank.

I would like to run a duplex cable from the rear battery to the switch panel. The total duplex run would be 32 feet and the total amp draw should be no more than 30.

I think I need a 10 AWG duplex cable for the 30 foot run and 16 AWG boat wiring for leads from the switches to the instruments (+) and bus bars (-)?

Does this sound right?

Thank you for any help you can provide.


Hi Tom,

I would recommend using my boat wiring size calculator to answer your wire size questions.

  • Leave the voltage drop percentages in column B and G alone.
  • Enter the current draw of you switch panel devices in column C and H.
  • Enter you total wire length run in inches for each device (switch to device and back to ground) in column D and I
  • Enter your total wire length run in inches for the panel feed (battery to panel and back to battery) in cell 25D – 384 is your guess.
  • Your wire sizes will be in Column E and J.

Let me know if you have any questions,


Wellcraft Wiring

Hi Kevin,

I’m considering a total redo of the marine electrical on my 1984 23ft Wellcraft Sportsman Walkaround.

I have a 200hp Mercury and the engine harness is fine as is the boat battery wiring and the switch wiring.

What I need to rewire is my navigation lights front and rear, anchor light, the two bilge pumps front and rear (with the option of adding one more in the rear) and docking lights also adding a few underwater lights on the transom. I also have a horn, washdown pump and trim tabs. I have one furuno 620 and two gps setups.Wellcraft Sportsman

What I want to know is if I order a boat wiring harness and switch harness from your sister marine electrical site, EzAcDc, will they cover everything I need? If not any help you could offer would be great.

Thank you


Hi Tom,

Thanks for considering some of the parts on our retail boat wiring site.

Our boat wiring harnesses contain wiring for an automatic bilge pump, a livewell pump, courtesy lights, navigation lights, docking lights, and a boat horn.

When combined with our switch panels, it is simple to connect additional electronics like your Furuno and your GPSs. Additional bilge pump wiring can be run from the pump to the switch panel.

We offer several boat battery switch systems to fit your needs. Our most popular is the smart marine battery switch system. Your 200 HP Merc will work great with this system.

Hope this helps. Thanks again.


Bot Buddies

Dear Kevin,

Last summer, I purchased a new aluminum fishing boat. It’s great, but I screwed up by “cheaping out” at the last minute. I passed on the trolling motor package and – as you’ve probably guessed – now want to add a trolling motor.

As a long time reader, I know that you are a big fan of Motorguide trolling motors and I’ll be buying one in the next couple weeks. My question concerns the boat wiring.

The Motorguide will be bow mounted, but since I didn’t get the trolling package, the only wire at the bow is a 16 gauge pair for the Attwood LED navigation light. But, according to your boat wiring size calculator, the trolling motor should be wired with 6 gauge.

Is there any way to make the smaller wire work? I hate to start rewiring a brand new boat if I can avoid it.



Hi Sean,

Since your boat is new, you may be in luck. A lot of boat builders now use Ancor’s new Nanotech Wire. As you’d guess from the name, it uses nanotechnology to solve problems just like yours.

Simply put, Nanotech Wire matches wire size to power demand by moving copper to where it is most needed – sort of a Viagra for marine electrical.

In the past, running a trolling motor on undersized wire caused voltage drops, heat buildup and embarrassing insurance claims. But now, that same temperature increase signals Nanotech Wire to deploy an army of nanobots who quickly rebuild the harness to match the power demand. While at work, these little guys make the wire looks like a python that swallowed a large rat.

Once your harness is properly sized, the same bots then go to work on its insulation so that it correctly corresponds to standard boat wiring colors.

The patented process is called Nanotech Overload Sensing Heat Induced Tranference and it works great. The only time I’ve seen it fail is when there are so many accessories turned on that there is no extra copper available. If this happens a lot, I usually recommend the addition of a copper reservoir to supply additional material as needed.

Have an excellent day.


Adding navigation lights and outlet

Hi Kevin,

Can you please help me with a fishing boat wiring question?

I need to wire a Mariner 40hp outboard to navigation lights and a 12 volt outlet.

Can you tell me how I wire the engine to the battery, the battery to fuse panel and then to switches and then to the Attwood navigation lights and outlet? Here’s my boat wiring diagram of what I’m trying to accomplish.boat wiring diagram

Yours sincerely


Hi Louis,

To start with, I would add a ground bus like these on our sister boat wiring site. You may already have on incorporated in your fuse panel.

Here are the basics for your marine electrical switches and 12 volt receptacle.


  • Constant power wire from fuse panel to navigation light switch.
  • Switch power wire from navigation light switch to navigation light.
  • Ground wire from navigation light to ground bus.

12v receptacle

  • Constant power wire from fuse panel to 12v receptacle.
  • Ground wire from 12v receptacle to ground bus.

Hope this helps,