Boat Battery Cables Get Hot When Cranking- Quick Troubleshoot

Sometimes when cranking, you can realize that your boat battery cables get hot. As it is normal for the battery to get hot after a long period of cranking, if the heat extends to cables can suggest there’s something else that needs to be checked. There are a number of culprits that can give rise to this complication.

Count yourself lucky if you are reading this article since we have researched a lot for you. The report provides various causes of boat battery cables getting hot when cranking problems and solutions to each complication. With such information, your life will be interesting and enjoyable; everything will be a breeze when boating.

Briefly, you should expect to come across reasons as to why your boat battery gets hot and possible solutions. More so, we will equip you with tips for betterment and finally frequently asked questions. Let’s ride together toward this handy guide.  

Why your boat battery cables get hot when cranking

After holding a thorough research, we came across several factors that might make your boat battery cables get hot when cranking. These culprits include;

1. Corrosion buildup

Why your boat battery cables get hot when cranking

I know someone is holding doubts whether it is possible for corrosion to cause hot battery cables. This is true since the terminals will not work properly as a result of corrosion buildup, creating resistance. This implies that the electricity flow will have to be interfered with, slowing its speed and making the cables hot.

As days go by, the effects of corrosion will extend to the lead terminals as they tend to be weakened, including cables. This is the main reason as to why you should act on the spot whenever you come across corrosion formation on your boat battery terminal. This problem is famous for also affecting the general performance of the boat since it may take extended time for the engine to start.

Cranking the boat for an extended time will eventually heat everything attached to the battery, including the cables, terminals, and the battery itself.

2. Faulty copper wires

Here is another factor that might be making your boat battery cables hot. Broken wires in the cables give rise to resistance as well. With such an issue, your cables tend to have reduced copper mass for a required electricity amount through the cables. This complication will eventually cause heat on the cables that can be a threat as the insulator may start burning.

It doesn’t matter the exact location of the broken copper wires in the cable, the whole cable will get hot. Since the wires and clamps are made of copper metals, heat will be felt directly from the cables to the terminals. The terminals will therefore become heated too. However, it’s not normal for cables to become too hot for a touch.

This is a clear indication that checking the condition of the cables once in while can be the best treatment for broken copper wires in the cable. Doing so will ensure everything works smoothly as it should. However, broken wires are faulty when the cables are too hot for a touch.

3. Rusted copper wires in the boat battery cables

After looking at the terminal corrosion buildup, let’s have a look at how rusted copper wires in the battery cables can heat the cables. These rusted copper wires are in front of creating resistance, overheating your boat battery cable. Heat is therefore transferred directly from the problematic cable to the battery that will eventually heat the terminals.

You have to understand that battery cables are manufactured from a combination of rubber and copper for substantial insulation. After a long period of usage, the rubber tends to degrade, leaving the cable with cracks. Nothing will hinder water from penetrating inside the cable; the copper wires will have no other choice, but to oxidize.

Corrosion is therefore experienced when copper and water comes in contact in the cables. This situation is famous for affecting smooth flow of electrons. Heat is always experienced whenever there is a resistance. Who knows! Maybe this is the exact disease your battery is suffering from.

4. Poor connection

The fourth cause of hot boat battery cables when cranking is the bad connection. This issue occurs, mostly either of the wires gets hot at a certain connection. Maybe the connection of the area is problematic. A clear symptom of this complication is that every electrical component in the vehicles goes off whenever you start the engine. Something bad has happened to your connection.

5. Faulty starter

Sometimes, you might be experiencing heated boat cables, but the engine is not turning over. In such scenarios, the big culprit to be held responsible is the starter. It might be worn-out or you are having a shorted big wire stretching to the starter. A bad engine or the starter causes too much current flow from your battery.

6. Overusing the starter

Besides the problematic starter, the cables might also get hot as a result of too many stars. This issue occurs mostly when the motor is spinning while you are trying to start the engine. The motor has failed and therefore you are overheating the boat battery cables with your too much starts.

7. Loose connection

Last but not least is the loose connection. When a loose connection is combined with the high electricity flow the boat is using to start, the cables will get hot. Sometimes the lead acid battery terminal can end up melting as a result of overheated cables. You can treat this disease by allowing the battery to cool. Determine the problematic part to see why the starter is not working properly.

How to fix boat battery cables get hot when cranking problem

boat battery cables get hot when cranking

Battery cables can be dangerous when you are diagnosing something that you cannot see; you will get hurt. Below is a complete guide on how to fix the problem;

Solution 1: Determining the age of the battery

I don’t know the model of the battery you are using, but the age of the battery plays a vital role in this healing process. Batteries like Optima Blue Top dual-purpose batteries are long-lasting.

Solution 2: Cleaning the entire connections

Whether it is on the lugs or terminals, make sure all the battery connectors are clean. You should make sure that any sign of corrosion buildup is eliminated for excellent performance. Besides, you should retighten all the nuts that secure the cables to the starter, battery switch, engine block, and the battery itself.

Solution 3: Resistance test

A multimeter is the best tool that you should have in hand when it comes to resistance tests. Here, the first clause may emerge, meaning that the power resistance in your boat battery’s negative cable joining the battery to the engine is faulty. On the other hand, this issue may still be experienced on the positive cable that links the battery to the switch.

Try installing marine-grade tinned-copper cables since they are the best and most reliable.

Solution 4: Conducting cables’ autopsy

Carrying out battery cables’ autopsy can be helpful to determine also if the resistance is high. The wires might be crumbling with black and brittle points. This is a clear indication that your cables are worn-out and requires a replacement. Eliminating corrosion buildup that gained a foothold can give rise to overheating that will eventually eat copper filaments.

Solution 5: Replacing the battery or cables

This step is only useful when your battery and its components are new. However, it may happen that you bought a cheap model. For those batteries and cables that have lasted for more than five years, replacing them can be the best solution.

Tips for betterment

Tips for betterment
  • Problematic cable can give rise to other complications like fire. This happens when the alternator attempts to pump electricity via the broken wire. Overheating will trigger combustion.
  • A fault negative cable is also famous for affecting the charging capability of the alternator.
  • Hot battery cables means that your boat is suffering from high resistance. You should therefore ensure that the battery terminals are properly tightened and clean.
  • While diagnosing a hot boat battery problem, you have to be much careful because a highly overheated battery cable may leave your finger with a burn. Give your bonnet some minutes before opening it.
  • Corroded terminals are famous for exerting resistance to the smooth electricity flow, causing heat. Eliminating the corrosion is therefore necessary to restore the normal performance of your battery.

You might be interested to read also our another comprehensive article of: Causes of Speaker crackling at high volume


  • What are the components of the battery terminals?

Battery components are usually made of lead. This is logical since the cathode and anode of the plates in the battery are made from the same metal. Lead is very powerful and that’s why manufacturers use it in such applications.

  • Can corroded wires in the boat battery cause heat on the terminal?

Of course yes. Resistance will be created, overheating the cable.


Cranking your boat consumes a lot of energy but for a short time. This impromptu high amperage consumption from the battery can be one of the overheating causes. Hopefully, you have benefited from our article. Hot boat battery cable should not disturb you anymore; identify the exact issue and then apply either of the provided solutions. 

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