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Is There a Difference Between Saltwater and Freshwater Motors?

Once you get into boating, you’ll discover that the possibilities are pretty limitless. With so much open water to explore, you’ll likely find yourself scouring your local area for the next new boating hotspot to bring your boat. But a word of caution - your boat might not be built for every environment you find.

More than anything, it pays to know what kind of motor your packing. Fresh and saltwater conditions can impact your motor in different ways, especially if it’s only built for one or the other. So, is there a difference between saltwater and freshwater motors? Find out here.

Freshwater vs Saltwater Motors

To be fair, both fresh and saltwater can cause damage to your motor. That’s why some motors incorporate parts and features that help them combat the specific damages they could encounter in these specific environments.

In freshwater conditions, your main problem would be mineral build-up. Freshwater is rich in minerals that can accumulate on various motor parts and obstruct moving parts. In saltwater conditions, your biggest problem would be corrosion. Constant exposure to saltwater can cause the development of rust that can eat away at various metal parts of your boat.

To combat these problems, both salt and freshwater motors incorporate a number of features and parts that help them work optimally in the environments they’re designed for.

Sacrificial Anode Material

They’re called ‘sacrificial anodes’ because they essentially take the brunt of water damage. They’re designed to prevent corrosion of metal motor parts by absorbing the damage through their unique and often more reactive electrical conductivity.

For saltwater motors, sacrificial anodes are made of either zinc or aluminum. Zinc anodes have been used for much longer, which is why anodes have gotten the nickname ‘zincs.’ These days though, aluminum anodes are becoming much more popular since their lighter and easier on the environment.

In freshwater conditions though, zinc and aluminum don’t perform well. Mineral deposits heavily accumulate on zinc, creating a thick coat that prevents the metal from doing its job. And while the same doesn’t happen to aluminum, it still isn’t efficient enough in freshwater.

For that reason, freshwater motors tout magnesium sacrificial anodes. So make sure to check. It also helps to keep an eye on your anodes since they will give in to all that corrosion over time. Making the necessary replacements when they’re tired and used up should help keep your motor in proper running condition.

Cooling System

Just like a car that needs coolant to save it from overheating, so too do boat motors require a cooling system. But unlike cars, they use water instead of coolant. Today, boat motors can use one of two cooling systems - raw water or freshwater.

The raw water system is found on freshwater motors. These systems take water straight from the environment it’s in. They cycle the water through the system and flush it out along with the heat from the motor. They’re ideal for freshwater conditions because freshwater is less likely to corrode the internal mechanism of a motor.

But since saltwater can cause rust to form inside a motor, then the raw water system won’t be ideal. Instead, the saltwater motor uses a freshwater system. This means that the motor has an on-board reservoir of clean water that it passes through the system to reduce heat. The fluid also mixes together anti-freeze for more effective cooling power.

Mounting Style

For the record - freshwater and saltwater motors can be either inboard or outboard. But there are certain factors you might want to consider that could impact whether you should get a motor that sits outside or inside the boat.

As the name suggests, an inboard motor is a motor that’s mounted inside your boat, usually below the deck. They’re typically designed so that you can’t take them out as easily, so any maintenance will have to be performed without removing the motor. For that reason, inboard motors are best used in freshwater conditions because they’re less prone to corrosion.

Outboard motors on the other hand, mount to the outside of your boat. They’re designed so that you can remove them pretty easily. This also means that any cleaning and maintenance becomes way less tedious, since you can work on the motor independently of the boat it mounts on. Obviously, this also means that outboard mounting works best for saltwater motors.

Can You Use Saltwater Motors in Freshwater and Vice Versa?

In general, saltwater boats are designed for more rigorous conditions. They’re built to withstand corrosion to a greater degree, so they don’t really do so bad in freshwater. That said, freshwater boats might not be tough enough to face the conditions of a saltwater environment.

But that doesn’t mean you can’t take them out for a spin on the sea. If anything, you should be able to take it out on a trip or two, but then it would entail flushing out the system with freshwater once you get back home. This helps clean out any saltwater sediments that might be left behind in your motor.

If you’ve been using a freshwater motor and you think you want to convert permanently to a saltwater set-up, then you might have to consider making a few changes. Those include:

  • Applying anti-foul paint
  • Installing a full-closed cooling system or a freshwater flush system
  • Changing magnesium anodes to zinc or aluminum
  • Replacing your bilge pump with a saltwater pump
  • Installing a mercathode system

Know Your Motor

Is there a difference between saltwater and freshwater motors? The obvious answer is yes, there is. But that doesn’t mean you can’t bring your boat out to a new boating spot every now and then.

Understanding the different parts and features that make a boat a fit for freshwater or saltwater makes it easier to prepare for the environment you’re heading into. With the right cleaning tactics and proper preparation, you should be able to maintain your motor wherever you decide to go.