Marine Ac/Dc attempts to answer your questions about boat wiring and marine electrical techniques, concepts, and products. We get lots of mail from folks in mid-project or who are just curious about their boat’s electrical setup.

There are loads of post already on the site which we hope you will browse through. If you’re trying to track down info about a more specific category, please use the search box in the upper right of this page or check out the list of various subjects farther down on this page.

If you aren’t able to find the info that you need to complete your particular boat wiring project, please send us an email at boatwiring@gmail.com.

Thank you for visiting. We look forward to hearing from you and hope that you will be able to come back often.

Kevin,

I’d like to take my portable icemaker with me to the coast. I have a 22 foot cabin cruiser with a 90 hp Honda and two series 24 batteries – and need your help figuring out the boat wiring.

The icemaker draws 2 amps at 230 watts, so it won’t be suitable for a small inverter plugged into my cigarette lighter….will it? I thought about just adding a larger wire to the cigarette lighter, but that wouldn’t help the plug itself.

The inverter says it should be wired straight to the batteries if the appliance is over 180 watts. Wouldn’t it be better just to put in another circuit on my circuit board with size 12 or so wire and a 5 amp fuse/breaker?

Thanks,

Henry

Hi Henry,

I would recommend running the new inverter wires directly to the battery.

Your existing DC system was not designed to carry the additional current that your inverter will draw. You may have excessive voltage drop or even wires overheating.

Please send pictures of your final install,

Kevin

Kevin,

When replacing my factory installed circuit breakers, I noticed the breaker for the bilge pump is only rated at 4 amps.

My Rule bilge pump, (also factory installed) is labeled “12 Volt 6 amp fuse”. The specifications I found on line say this pump draws 3.3A at 12 volts and 5.0 amps at 13.6 volts. I assume the boat wiring size used is typical for bilge pump installation. (appears to be 14-16 Ga.?)

Should I install a larger circuit breaker with this set-up? I am thinking a 7 Amp would be sufficient?

The boat is a 2002 Sea Pro 235 WA with two batteries.

Thank You

Shonna

Hi Shonna,

I would go with the 7 amp breaker.

7 amps will not exceed the current carrying capacity of your wire, will help reduce nuisance tripping of the breaker under full load, but will trip under a locked rotar condition.

Thanks

Kevin

Hello Kevin,

I am looking to find a boat wiring diagram to rewire my 1996 17 foot Key West boat.

I will need the complete wiring schematics for this model. Do you have this information or can you tell me where I can find it online and print in order to start my repairs tomorrow?

Thanks for your help, I look forward to hearing back from you

Marco

Hi Marco,

I’m sorry, but we do not have a boat wiring diagram available for your boat and you will probably not find one.

But, this list of standard boat wiring colors for marine electrical should get you close. Most boat builders have been using this code or one very similar for over twenty years.

Kevin

Kevin,

I am building a 16′ wooden bass boat using the Glen-L design and it is about 80% complete. I am now getting ready to outfit the interior, build the helm, purchase my motor, etc.

I have visited your sister boat wiring site and it looks like just what I will need due to its simplified “plug and play ” approach. What I am looking for is advice on everything I will need to wire my boat using EzAcDc marine electrical.

My boat wiring needs include:

• On /Off
• Navigation lights (2 for bow red and green plus one for stern white)
• Power winch connection for my anchor
• Boat battery cable (2 batteries)
• Electric trolling motor connection
• Wiring to connect rope lighting
• Stereo connection
• Fish finder at bow
• Fish finder / chart mapper on the helm
• Connection for an electric boat horn
• Power outlets for spot light and for plug in portable bait well pump / aerator
• Battery switch system with wiring
• Various gauges (voltmeter, speedometer, battery condition meter, etc.)
• Bilge pump wiring for two pumps

In summary, I need everything and look to your recommendation to help me get what I need to fully wire my boat from the boat wiring harness to fuses, circuit breakers, switches, etc.

Thank you.

Kelly

Hi Kelly,

Your boat sounds great! Thank you for your interest in the products at our sister site.

Here is the boat wiring that I would recommend.

• Fully wired eight switch marine electrical panel. This comes with one panel mounted 12 volt receptacle and you will want to add a second remote outlet.
• Boat wiring harness that quickly snaps together with the panel above.
• Smart Battery Switch system for two batteries. This includes cables, ground bus, and you will want to add a couple of battery boxes.
• Navigation lights are controlled by the nav/anc switch in your new switch panel. Wiring for split red and green lights and a single white stern light is included with the boat wiring harness. The site has a variety of Attwood LED navigation light kits that may suite your needs. All come with connectors so that they will snap right onto the new harness.
• I would run 8 AWG tinned wire for your trolling motor.
• Please send me the specs and length of total wire run for the power winch to determine the cable size requirements.
• Currently we do not stock a trolling motor connection. My preference in the Marinco Connect Pro System.
• You can use one of the switches on the new panel for the stereo. The new panel will even include a pre-printed “STEREO” switch cap. There is a ground, constant power (memory), and switched power coming off of the back of the switch for a stereo. We do not include speaker wire.
• The boat wiring harness has two breakouts for courtesy lights. The switch panel kit also includes a “COURTESY LIGHTS” switch cap.
• We do not have fish finders, but you can get power for your fish finder from one of the breakers on your new switch panel.
• The switch panel comes pre-wired with a horn button and the boat harness includes wiring for a horn.
• We also have boat horns that will attach easily onto the new harness.
• We do not have gauges. Most of the gauge wiring will be included with your engine harness.
• Our harness comes with one bilge pump and auto float switch connection. You can either run a second pump from one of the switch panel accessory wire breakouts or you can use the livewell pump breakout for a second pump.
• No additional fuse panel is needed. The switches have circuit breakers mounted directly below them on the panel. The main harness battery connection has an in-line circuit breaker for harness protection.

Thank you again for your consideration. I hope this helps,

Kevin

Kevin,

My boat anchor winch is the Deck Mate 19 Small Boat Anchor Windlass from West Marine. The draw is 15 amps @ 12 volts and the winch includes a built in 15A circuit breaker. The length of wire from the helm to the power winch at the bow is roughly 9 feet. Please advise cable size requirement.

Thank you.

Kelly

Hi Kelly,

18′ run total @ 15 amps with 3% drop, I would run 10 AWG wire.

Kevin

Kevin,

I have to replace a wiper motor which has only two wires and an “on and off” switch.

I’m going to replace with a AFI MRV #34000 which states I need a three-position switch. This would be very difficult to rewire though the windshield.

The vessel is a 1991 SeaRay 350. Is it possible to us the existing switch and boat wiring??

Gary

Hi Gary,

If your current wiper has two wires, power and ground, connect the ground to the case on the MRV 34000 and the power to either speed 1 or speed 2 on wiper motor.

If your current wiper has three wires, power, park, and ground, connect the ground to the case, park (constant power from fuse or breaker) to the park wire on the wiper motor, and the switched power to either speed 1 or speed 2. Even though your new wiper motor has two speeds, you will only be able to control one.

Hope this helps,

Kevin

Hi Kevin,

Quick question.

I am going to buy and install sidewall lights for a friend’s cabin. The locations are prewired.

Could you please tell me if there are any specifications that I should be aware of? Since these will be running off the battery, do I have to get DC specific lights? Any recommendations as to the boat wiring?

Thanks,

John.   

Hi John,

You will need to buy DC specific lights. You will also need to know if the system is 12 or 24 volts. The higher voltage lights will illuminate at the lower voltages, but will be dim. For example, 120v lights will operate at about 10% output if a 12v supply is applied. They would last forever, but would be dim. Too low a rating, they would be bright, but short lived.

They will be labeled in the form…12vdc…10 watt.

Hope this helps,

Kevin

Hi Kevin,

I’m redoing the boat wiring an my old 1978 Catalina 25 sailboat.

I need to know which gauge of marine electrical battery cable to use in connecting the batteries to the boat battery switches and the switches to the boat bus bars. The overall distance for the wire runs is no more than 48”.

Thanks.

Brice

Hi Brice,

This will depend greatly on the loads.

If you have a simple DC system and no starting motors, then you could use 4 AWG battery cable. If you use these batteries to start an engine or you have a large DC load bank, I would go with at least 2 AWG battery cable.

Hope this helps,

Kevin

Hello Kevin,

I’m beginning a large boat wiring project on my 38 foot sailboat.

I have purchased new marine electrical panels and switches, and am beginning the wiring plan.

I need to know how to properly support the wires. For example, is conduit to be used…wrap around protective sheathing? The existing boat wiring (which was automotive wiring), had large lengths of wrap around plastic protective sheathing that looked to be flammable.

Please advise.

Thank you,

Earl

Hi Earl,

Per the ABYC, American Boat and Yacht Council, boat wiring must be supported every 18″ and any loom must be self extinguishing.

My preference self-extinguishing, split loom with cable ties every 12-15″. Make sure to add cable ties on each side of marine electrical bus bars and modular connectors. Even though these terminals are required to resist a 6 lb. pull test, it is better to take the extra time in installation than waste your time troubleshooting.

FYI, usually a blue tracer line on the split loom signifies self extinguishing.

Happy wiring.

Please send pictures of your project.

Kevin

Kevin,

Your Easy Add AC – Marine Shore Power looks fantastic. Just what I need to plug and play!

I need some advice on the green ground wire. I have a DC system. No engine on my sailboat. Want to add your AC shore power system.

Your instructions state to connect to my DC negative which in turn on most boats is connected to the engine which provides ground. How do I accomplish grounding without an engine? Seacock, ground plate?

Thank you,

JR

Hi JR,

I’m glad that you like our system. As you said, we designed it to be truly “plug and play”.

As for your question…

The green AC ground wiring should be connected to the negative side of your DC system. This provides a low resistant path to ground in the event of an AC to DC fault. Even though the 5 mA GFCI on the panel will trip long before the 30 dock main, we still need to have the green AC grounding wire to keep our friends at the USCG happy.

Hope this helps,

Kevin

Hi Kevin,

Thank you for the prompt reply.

I’m still confused. Is it ok that the DC is not connected to an engine (no engine on my sailboat)? Do I need to connect my DC bus to a seacock or external ground plate?

Thanks,

JR

Hi JR,

If you have a grounding system on your boat wiring (ground plate, seacock, etc), it should be connected to the DC negative system. The AC grounding wire from your AC system should connect here as well.

This will help prevent your seacock from being energized by 110v AC with no low resistance path to ground.

Kevin

Kevin,

Just to get it straight —the seacock and the AC green and the DC negative all connected to the DC neg bus? The seacock which is is on the water side provides the low resistance path ?

Thanks in advance for your tolerance. BTW you make it an easy choice to purchase from your boat wiring store with such great tech advice!!

JR

Hi John,

The wire that connects the AC grounding wire between the AC panel and your boat’s grounding system provides the low resistance path to ground that will trip the breaker on the dock. Without this, in theory, an AC wire can accidentally come in contact with the seacock on your boat. Since there is so much resistance the water, the dock breaker will not trip due to the low current the seacock path to ground (through the water) is inducing.

If a swimmer comes near the seacock, they become a lower resistance path to ground (the bottom of the marina) and then become paralyzed by AC voltage present in the water.

The main GFCI on our panel protects far beyond what the main dock breaker can do.

Hope this helps,

Kevin