Tunnel Hull Rewire

Hello Kevin,

I am in the middle of the complete rebuild of of an older 19′ tunnel hull CC.

I am rapidly approaching the dreaded marine electrical portion of the job and I am thrilled to have stumbled upon your sister boat wiring site, EzAcDc. As I piece together the marine electric items I think I will need, I am requesting your assistance.Mako Tunnel

My outboard power is a 90HP Merc Optimax.

I would like to run dual batteries with a smart boat battery switch system. I need to run navigation lights, bilge pumps, and a hydraulic jack plate via the switch panel. I would prefer to add docking lights also operated by the switch panel and at least one 12 volt outlet.

I prefer to run two bilge pumps on separate auto float switches operated by a single panel switch. Additionally, I see the switch panels that come with 12V outlets, but do you sell 12V remote outlets by themselves?

So far, I am looking at the following:

  • Complete Smart Marine Battery Switch System
  • Snap Together Boat Wiring Harness
  • Snap Together Five Switch Marine Electrical Panel
  • Attwood LED Navigation Lights
  • Attwood 500 GPH Automatic Bilge Pump System. Two of these if I can run them on the same switch (5amp?)

Here are my questions:

  • Will my bilge set up run on a 5 amp switch? Jack plate?
  • Should a 10 amp ACC switch run any reasonable headlight setup?
  • Battery recommendation?



Hi Hank,

  • I would not recommend running two bilge pumps with the same switch. If you add a second pump, you will run the risk of nuisance tripping the circuit breaker when both pumps are running. If you increase the size of the breaker, you run the risk of not tripping the breaker if the pump motor gets clogged and locked.
  • Most jack plates operate with a momentary up / off / momentary down. They actuate a relay system that comes with the power jack plate.
  • The 10 amp accessory circuit will accommodate a pair of 55 watt halogen lights. Most docking lights are either 35 watt or 55 watt.
  • You may want to consider switching to the eight-switch marine electrical panel to have room for all of the switches that you are considering. You would have enough switches for two separate bilge pumps, docking lights, jack plate, etc.
  • I have always been a fan of the classic Interstate battery. The HD24-DP is a good all-round battery. The Optima Blue Top is also a great battery choice.

Please let me know if you have any questions,


Boat Battery Wiring Size


I’m in the process of installing the automatic smart boat battery switch that you designed for EzAcDc Marine Electrical.

On your boat wiring diagram it shows that the boat battery wiring coming from the batteries to the marine battery switch, are 2 AWG ( red & black). The wires coming from the switch to the VSR are 8 AWG.

The cable from my motor, a 50 HP Mercury, are 6 AWG.

Do I use the size wires as shown, or can I use a 6 AWG throughout the complete wiring ?

Will it still work safely ?



Hi Rob,

As you increase the boat battery cable length, you will need to increase the boat battery wiring size to reduce voltage drop.

Mercury provided 6AWG cables with your motor with the assumption that it would be connected directly to a battery or to a boat battery switch with minimal voltage drop. If you use 6 AWG cables from the marine battery switch to the batteries, you will induce a larger voltage drop and may cause your engine to not start.

Running 2 AWG from the batteries to the switch will help reduce the voltage drop to the engine. Another option would be to run 4 AWG from the engine to the battery switch and 4 AWG from the switch to the batteries.

Hope this helps,


Bertram Refurb


I am currently restoring and repowering a 20′ Bertram.

The boat is a stern drive with both batteries in the motor box. I have already purchased an automatic smart battery switch and an eight switch marine electrical panel.Bertram Moppie ad

This boat helm is very far forward. The boat will be used exclusively in salt water and I want to have a very “heavy duty” boat wiring job. All the equipment will be run to the forward helm and some accesories like

  1. Bilge pump
  2. Diaphragm pump
  3. Washdown pump
  4. Bilge blower
  5. Navigation  lights

…will be needed to run back to the motor box. All other accessories will be mounted near the forward. helm.

Here are the other accessories on the marine electrical system:

  • Stereo
  • Boat horn
  • Engine room lights (also run to the stern)
  • Gunnel lights
  • GPS
  • VHF

I need a harness to accomodate all of this.

Your thoughts?



Hi Marshall,

To do this job correctly, I would recommend that you build a completely custom boat wiring harness. The best place to start is with our wiring size calculator. Use this to determine what size wire your components require along with the size of the panel board feed wire.

Tinned wire in standard boat wiring colors and most sizes is available on our sister marine wiring site.

Good luck with the project. Please send pictures of the electrical portion of this restoration and we will post them on our site.



Glen-L Wiring


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.


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,



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.


Hi Kelly,

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


VSR + Charger?


I recently got a Smart Boat Battery Switch system from your partner marine wiring site, EzAcDc.

The Smart Switch seems great and should work really well on my boat. I do a lot of fishing and after running the trolling motor for a long time, often worry about having enough power to start my outboard. Your system seems to be a perfect solution.

But, I have a question:EzAcDc offers a VSR based Smart Battery Switch for your boat wiring project

After boating all day and parking the boat, is it still ok to charge the batteries the same way? In my case, I’ve always used an on board charging system utilizing 110 volt home current. Will that still work?

Thank you,


Hi Josh,

I’m glad that you like the smart battery switch that we put together. It’s designed to alleviate exactly the concern that you have had about boat battery management.

As for your boat wiring question…

Yes. You can use the charger just like you have in the past. Just as with your alternator charging while underway, the VSR will connect your battery banks as the voltage in your system rises. So when you are ready to head back out, both battery banks should have a full charge.

As for multi-stage chargers, like the Guest line, almost all can be plugged in indefinitely and not overcharge you batteries.

Happy boating,