Nobody likes constant nagging electrical problems on the water. Investigating a voltage issue costs more time than one would think and can be a frustrating endeavor. Using the correct marine fuse block, wiring, and marine circuit breaker, luckily, can alleviate most of these woes.
The most important aspect of a boat’s power supply is, of course, the battery. We highly recommend the Ionic Lithium 12v 125 Ah battery as both a cranking battery and the power to the boat’s electronics. In the vast majority of boats, this single battery will run all of the units with zero problems. The only exception to that MIGHT be someone running six total units plus a forward facing sonar module. In that case, we would recommend running a dedicated electronics battery, preferably a 125Ah. For everyone else, the single big cranking battery is just fine and will have more than enough juice.
FOR SURE, we want power to be ran independently of the rest of the boat’s systems. This means we will not be using any factory installed wiring harnesses. In the vast majority of boats the factory wiring simply isn’t enough OR the power has to run through relays which are unreliable. Instead, we will install 6 AWG ancore marine wire that runs direct from the battery to a 30 amp marine circuit breaker or a 40 amp marine circuit breaker, then to a battery disconnect switch (our favorite is the blue sea 6006 m-series), then to a marine fuse block (specifically a blue sea fuse block). The use of a marine fuse block is not a necessity as 12v in line fuse holders come with most marine electronics. We just prefer to use a marine electrical fuse block due to the convenience of having all fuses easily accessible and located at a single place in the boat.
The purpose of the marine circuit breaker is to save the boat and battery in the case of a short, which could happen due to mice or some other unfortunate event. While a marine waterproof circuit breaker can be used as a battery disconnect, we recommend using a normal battery disconnect switch behind the breaker. The circuit breakers are generally not designed to be flipped much as an on/off switch and using it as such could potentially cause it to fail. The size of the circuit breaker just depends on the electronics used. One look into the specs of the units and we will find amp draw. Combine the amp draw of all electronics going through the breaker and we should find what size it should be. Again, a 30 amp marine circuit breaker or a 40 amp marine circuit breaker are typically our choices here.
The location of the marine fuse block, and if to use one, is mostly up to the convenience of the boat owner. Some anglers would prefer to run 6 gauge ancor marine wire to the starboard rod locker and branch off from there. My personal boat, on the other hand, has a blue sea fuse block in the rear compartment by the batteries. I only did this because my starboard rod locker stays full of gear. Either avenue is acceptable. I use a BLUE SEA 5029 ST BLADE FUSE BLOCK and an independent ground bus. Blue Sea also makes a fuse block complete with its own negative bus. Again, either way is perfectly acceptable.
From the fuse block, we run 10 AWG ancor wire to each individual unit. Size 10 is just a touch bigger than necessary in most cases, but we find its better to be overpowered than underpowered. Using wire that is too small will result in a drop of voltage from the battery to the unit. This can all be calculated as well if necessary. And remember, if using a fuse block, the in line fuses are no longer necessary and should be done away with.
The importance of good connections cannot be understated. Many boats we see with power issues have poor connections. We use quality heat shrink terminal connector of the correct size and make sure they are all properly fastened and heat shrunk to the wiring. On the bigger 6 awg wiring we will crimp on the proper size cable lugs and then add adhesive lined heat shrink tubing. From there, every connection, including our fuses, will have deoxidizing electrical grease added to prevent corrosion.
Rigging a boat correctly the first time is the best option to go out on the water worry-free, but even redoing a previously rigged boat can be well worth it in the long run. The cost of proper electrical wiring and equipment is minimal compared to the headache and time cost associated with an improper set up. For any questions on boat rigging, electronics, and more, give us a call at (325) 269-1882.
