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,


Sled Boat Wiring


I have a basic 16.5 aluminum open river sled with a single engine. Currently the motor runs off one 12v battery with a manual bilge pump switch hooked up.

Koffler River Boat

I would like to add a second battery for:

  • Electric trolling motor
  • Navigation lights, to be installed
  • Bilge pump to this battery
  • Fish finder
In addition I would like to add a 12 volt two bank marine electrical boat battery charger for both batteries. I will add a 6 position fuse panel to the mix.

My questions or concerns:

Any interaction between the 12vdc system and the 120v battery charger to insure that I don’t get a ground fault. Would adding a battery switch assist with this potential problem or will a bus bar be necessary?

Thank you for any input,


Since your system is 12 volt only, I would connect all of your grounds together, including your batteries, at a common bus.

You will only trip a ground fault outlet if there is a fault from ac hot to boat ground and the boat is connected to earth ground.

If this happens it will not matter if you have a battery switch or not.

Hope this helps.


Crestliner Wiring Upgrade


Could you please check out my homemade boat wiring diagram? It’s for my 17.5′ Crestliner Fish Hawk.

As you can see, I added and wired the two Attwood battery selector switches and a fourth battery to the system (Battery 2) and wired all the batteries in parallel. I also added the Blue Seas fuse block, all lighting, fishfinder, trolling motor, etc.

Crestliner boat wiring diagram
Click to Enlarge

My goal here is to be able to run the trolling motor off the extra battery if needed and/or to be able to start the motor with the extra battery if the main died. Also, to run all the lights off the extra battery for night fishing. I’ve yet to turn both switches to “both” because I’m not sure if that would be bad for……..everything.

I’m obviously an amateur at this so was wondering if you think it’s a safe setup assuming all the fuses, connections, wire gauge, etc. are kosher? I haven’t had any trouble yet but I’m a little nervous about burning something up.

I’d really appreciate your input if you can decipher the wiring diagram.




I would make a couple of minor changes:

  • Move the trolling motor circuit protection to the trolling motor side of the switch.
  • Add circuit protection for the Blue Seas fuse panel at its connection location to the boat battery switch.
  • Use the same size boat battery cables for all of your battery link wires. You call out 4/0 for the positive lead (I would assume you mean 4 AWG) but not on any of the other cables.
  • If the trolling motor batteries are near the bow of the boat I would consider adding circuit protection at each end of this wire to help reduce the risk of a catastrophic fault.

Hope this helps,



Thanks for the help Kevin. I’ll do all of that.

Also, I was wrong about the battery cable being 4/0, its actually 1/0 welding cable.
Thanks again,



Most people don’t use welding cable on boats or cars because it is not oil resistant.