Boat Wiring Harness: All You Need To Know Before Buying

A custom boat wiring harness is critical to the organization and safety of your boat’s electrical system. Custom wire harnesses take lengthy wiring setups and make them feasible for fitting into a secure, finite space. The right custom boat wiring harness will take miles of wires and safeguard them in a structured fashion. 

A large number of wires can pack into a single custom boat wiring harness. These wires have a coating to protect them and are put together with a band, sleeve, tape, or lacing.

Custom wiring harnesses take your boat’s particular wiring challenges into account. Your boat will function at its pinnacle of safety and electrical efficiency with the right custom boat wiring harness.

Chapter 1: Understand Boat Wiring Harness

1.Why boat wiring harness is important

A proper boat wiring harness secures your boat’s electrical wires and safeguards them against vibrations, moisture, and abrasions. Because boats do most of their work in the water, it’s crucial to protect your wiring from the obvious pervading threat of moisture. It’s also essential to keep your wires organized and safe from jumbling with others by the boat’s vibrations as it moves.

A custom boat wiring harness is a critical investment in the electrical functionality of your boat. Everything from lights to radio signals needs proper electricity to keep them working. A custom boat wiring harness is essential as it serves to protect its efficacy.

2. What boat wiring harness is used for

A boat wiring harness has many uses. One is to protect your boat’s wires from environmental factors which could place them in danger. The right custom boat wiring harness will also organize your wires and pack them into a neat, finite space.

Without a boat wiring harness, your boat would leave a mess of wires unprotected from the dangers of water and vibration. One false move and one of your boat’s key electrical functions could compromise. A custom boat wiring harness will eliminate that worry and help your boat run at its peak capacity for much longer.

3.Boat Wiring Harness Color Code

Because your boat’s wiring is so complicated and should organize efficiently, your custom boat wiring harness should be color-coded for protection and ease—the harness groups different colored wires about their functionality and power. For example, light blue wires are usually used for the boat’s oil pressure reading and gauge.

The right custom boat wiring harness will color-code your wires to eliminate confusion and protect your boat’s electrical system. If there’s a problem with an aspect of your electrical system, you can easily find the wires which cause the trouble. That’s what a proper custom boat wiring harness will do for you.

Supply boat support oil and gas industry

Chapter 2: How Boat Wiring Harness Improves Your Boat

A proper boat wiring harness improves your boat’s electrical system and overall functionality in many ways. It’s number one function is to protect your investment in your boat’s electrical wiring. It groups like wires together in a color-coded fashion to make future replacement of wires easier. It also protects all of your wires from the elements so that they work at peak efficiency for longer.

The right custom boat wiring harness takes hundreds upon hundreds of wires and fits them neatly into the finite space of your boat. A boat wiring harness makes things easy on a boat’s owner. You won’t have to trip over loose wires or tack them up in odd, unorganized formations. Your custom boat wiring harness will serve to keep them neat, safe, and out of harm’s way.

Your boat’s organization and safety will both improve the use of a proper boat wiring harness. No boat owner should invest in a boat with an unsafe, unorganized wiring setup. The perfect custom boat wiring harness improves your boat as both an investment and a vehicle.

Close up the rear side of boat transom four-stroke outboard motor

Chapter 3: Signs You May Need Custom Boat Wiring Harness

If you build a boat, you’re going to need a custom boat wiring harness. As soon as you start to realize just how many wires it takes to make your boat run, a boat wiring harness becomes essential. If you don’t purchase a stock boat with boat wiring harnesses already in place, it’s a sign that you need a custom boat wiring harness.

Any vehicle which relies on electricity for functionality needs a wiring harness to safeguard its wires and electrical setup. This is especially crucial for boats. A custom boat wiring harness organizes and protects your wires from key environmental dangers. Since your boat will be in the water more often than not, a custom boat wiring harness is an absolute necessity.

Once you see the sheer amount of wires it will take to power your boat, you’ll know your need for a custom boat wiring harness. Without proper protection and organization, your boat’s functionality and overall condition will be in massive jeopardy.

Chapter 4: How To Build A Wiring Harness For A Boat

When you hire a company like CLOOM Tech to build your custom boat wiring harness, they’ll work first to organize your wire types. They will use an easy-to-understand color-coded system to ensure each set of wires for each particular need organizes. They’ll group these wires accordingly for ease of replacement when an inevitable power failure happens down the road.

The right company of custom boat wiring harnesses will safeguard your wires in harnesses that are moisture-resistant. Furthermore, they’ll build custom boat wiring harnesses that ensure that the vibrations of your boat don’t disconnect them or ruin them.

The proper way to build a custom boat wiring harness is with the safety of your boat’s passengers in mind. The right company of custom boat wiring harnesses will work to make harnesses that ensure no one trips over wires. Furthermore, the perfect boat wiring harness will vastly decrease the potential for electrical fires onboard.

Chapter 5: What To Look For In A Boat Wiring Harness Company

The perfect boat wiring harnesses company will have ample experience in the boat wiring harness field. There are a particular set of challenges specific to boats that you need to consider by your wiring company. If you work with a company that builds wiring harnesses but not for ships per se, you’re bound to run into wiring organization and safety problems onboard.

Don’t settle on a low-priced budget wiring company for your custom boat wiring harnesses needs. Look for a company like CLOOM Tech who has spent years upon years in the custom boat wiring harnesses business. Your initial investment in custom boat wiring harnesses will save you money down the road in electrical problems. 

Colorful wire harness and connector housing

The perfect boat wiring harnesses company will charge you fairly for a job that you won’t have to repeat or tinker with. Spend your money right the first time and get proper, safe custom boat wiring harnesses installed.

Chapter 6: Where To Buy Custom Boat Wiring Harness

There are a wealth of wiring companies online that claim to build proper custom boat wiring harnesses. Don’t let rhetoric fooled you. Look for a company like CLOOM Tech with years of experience in the custom boat wiring harnesses business. A standard wiring company will not understand the nuances necessary for building proper custom boat wiring harnesses.

Your boat is a massive investment and requires a wiring setup that takes its particular idiosyncrasies into account. If you go with a budget wiring company, chances are they will try to build boat wiring harnesses that don’t fully work with your boat’s set of structural needs.

Don’t buy custom boat wiring harnesses from a company that doesn’t understand boats. Find a company that has serviced thousands of boat owners and has left them satisfied with the quality and efficiency of their work.

Bunch of wiring harnesses

Chapter 7: How to Wire a Boat

Boat electrical wiring is a whole different ball game from wiring a home or even a car. The wiring must withstand excessive moisture, unusual vibration, high temperatures, and salty water. If you do not wire the boat’s electrical circuit to mitigate against these factors, there is a risk of equipment failure and, in the worst case, boat fires. 

This is why hiring a boat is not truly complete if it does not include boat wiring harnesses. Let’s take a closer look at how to wire a boat.

1. The Battery as the Electrical Source

A boat will have one or more batteries either charged by the engine’s alternator or the auxiliary battery charger. The batteries are the source of electrical energy and can generate hundreds or thousands of amps, more power than an entire house needs. For this reason, take all appropriate circuit protection precautions.

Boats would usually have two types of batteries–a starting battery and a deep cycle battery. A starting battery has a high current rush capacity, while the deep cycle battery can perform a deep discharge without causing any harm.

The two most common battery setups are the single-engine (one starting battery and one house battery) and the twin-engine (two starting batteries and one house battery).

2. Marine-Grade Main Battery Switch

Your boat wiring system should usually have a marine-grade main battery switch. For a 1-2-BOTH type switch, both battery positives run through it, allowing you to choose the battery you would like to output. Though this is similar to the A-B switch, the 1-2-BOTH allows you to parallel the two batteries. With that, you can turn off everything in a single action. 

You could use both settings when running your engine and looking to change both batteries from the alternator. You may also use the two settings to parallel your batteries during an emergency to start the engine after your battery is too depleted.

When the engine is off, remember to turn the battery switch to the house circuit, so you are only tapping into the deep cycle house battery.

Note that your best bet is the double pole ON-OFF-COMBINE battery switch for a two-battery, single-engine boat wiring system. It allows the start battery to stay isolated except during emergency conditions.

3. Bypass Main Battery Switch for Bilge Pump Float Switch

It is fairly standard boat wiring practice for electricians to bypass the main battery switch for one reason–the bilge pump float switch. With that setup, the pump will kick in if the boat starts to fill with water, even though the battery switch may be off. The rationale here is you would rather have a dead battery than a sinking boat.

Make sure you circuit-protect the fuse via an inline fuse. Pay attention to the bilge pump’s negative return wiring.

4. Get the Source to the Boat’s Helm

Next, source power from your house battery to the switch panel. Use a marine-grade primary wire to run a positive from the battery switch and a negative from the battery negatives (ganged together) to the central switch panel. 

This can be a fairly long wiring run. Bear in mind that the further away your battery is from the switch panel, the greater the voltage drop your wiring has to contend with. You can minimize the voltage drop by using a large cable. 

Also, the two conductors are typically thick as they have to carry your combined electrical loads. For small boats, 12 AWG wires would work. In larger boats, 10 AWG is normal. 8 AWG is overkill except for boats that are 30 feet or longer.

Note that if your switch panel does not come with circuit breakers, you will need a fuse block right before the panel and then conductors from each panel to each fuse. Many boat electricians recommend ordering circuit breakers with your switch panel to make installing and maintaining the panel easier.

Whether you are using circuit breakers or fuses, these overcurrent protection devices should be installed as close as is practically possible to the circuit’s power source. 

The main house battery positive conductor feeds directly to the switch panel. On the other hand, the negative goes to the negative busbar, where you eventually attach the load negatives.

5. Install Terminal Block

When you wire the switch panel, it will be easier for you to install the boat wiring harnesses with pre-installed heat shrink labels and ring terminals. This fits onto a terminal block.

Crimp a #8 ring terminal on your positive load wiring running around the boat to various loads. Each switch output has its own gang on the terminal block. With labels already in place, it simplifies the process of troubleshooting or adding items later on.

6. Load Wiring to Busbar and Terminal Block

From this point onward, the wiring is relatively straightforward. Connect your boat wiring infrastructure to the busbar and terminal block. Negatives go to the busbar while the positives to your terminal block. 

You would mostly use #8 ring terminals for termination. Ensure you install the positives on the right gang associated with the corresponding switch for the load. You can install the negatives on any busbar screw since the goal is to get them to the appropriate negative post of the battery.

There is nothing quite like the marine environment to push electrical circuits to their limits. Getting the wiring process right and using boat wiring harnesses is key to a boat electrical circuit’s quality and resilience. 


If you want to safeguard your boating investment, contact CLOOM Tech today. They can install custom boat wiring harnesses that ensure the safety and efficacy of your boat’s electrical system. They have a wealth of combined experience in the field of custom boat wiring harnesses, which will ensure your overall customer satisfaction.

If you settle on a budget wiring company to install custom boat wiring harnesses, you’re in for problems. There are just too many variable factors to boat wiring to entrust your boat’s electrical system in their hands. CLOOM Tech understands boats. They understand custom boat wiring harnesses.

They understand just how important the functionality of your boat’s electrical system is. When installing your custom boat wiring harnesses, they’ll do it with ingenuity and safety. CLOOM Tech anticipates wiring challenges before they become problems. Contact us today to get the right custom boat wiring harnesses installed the first (and only) time.

Hey, I am John, General manager of Cloom and OurPCB.

I am a responsible, intelligent and experienced business professional with an extensive background in the electronics industry.

Reach me at to get a quote for your projects.

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