The Main Differences Between Salt Water vs. Fresh Water Boating

North America has accounted for 46% of the global revenue for leisure boating over the last couple of years. In the United States in 2019, more than 87 million adults took part in recreational boating. Given that 71% of the planet is water, these figures shouldn’t surprise us!

A common question from new boating enthusiasts is, can you have one for both fresh and saltwater? After all, only 3% of the Earth’s water is fresh.

As we explore the salt water vs. fresh water boat discussion, we’ll consider topics such as hull design, hull fouling, corrosion, and whether you can use a saltwater boat in freshwater (and vice versa). So, if you’re interested in learning more, just keep reading!

Hull Design

Those new to boating may be unfamiliar with the structural differences between the various boat types. But when you think about the environments that you may face on a river or lake and compare them to those out at sea, you can get an idea of why these differences exist.

The hull design is one such difference. These boats typically have a V-shaped hull to allow them to cut through the waves and therefore add stability. Saltwater involves choppier and deeper water that will hit the boat repeatedly with a lot of force.

As freshwater is shallower and tamer, the V-shape doesn’t serve the same function. Boats with this shape are likely to scrape along the bed of these shallower waters, so they are often flat or rounded instead.

Hull Fouling

Fouling refers to the build-up of plant and animal life on your boat. It happens to any structure or vessel that spends time in the water. But when it comes to salt water vs. fresh water, we find that those in the sea are most susceptible to fouling.

Fouling comes in two forms: microfouling (tiny organisms such as bacteria and algae) and macrofouling (such as barnacles and seaweed). 

Seawater vessels benefit the most from the use of anti-fouling products.

Resistance to Corrosion

Most of us are familiar with rusting – where water catalyzes the reaction between oxygen and metal, turning it reddish-brown as it begins to disintegrate. This is a form of corrosion that typically happens with iron, but when we add salt to the equation, the damage is much worse.

Saltwater corrodes metal five times faster than freshwater!

When discussing salt water vs. fresh water boats, we can begin to understand why saltwater boats have such a different design. Any metal that interacts with the water, including sea spray which can get anywhere and everywhere, needs to be corrosion resistant.

One of the simplest and most effective ways of reducing corrosion damage to your boat is learning how to clean boat after salt water use. Especially if it’s been out at sea, as an after salt water boat wash can remove the salt and limit the corrosion damage.

Cooling Systems

One of the most notable (and important) differences between the types of corrosion resistance is found in the engine cooling systems.

To stop a boat engine from overheating, a pump pulls water into the boat via a seacock fitting. This cold water circulates the engine, allowing a heat transfer to take place which cools the engine by heating the water. It then leaves the boat via the exhaust.

Saltwater boats use an enclosed cooling system that uses fresh water and a coolant within a small tank located above the engine. When the seawater enters the boat, it doesn’t interact directly with the engine, but instead travels through a heat exchanger jacket and cools down the freshwater which has absorbed heat from the engine.

Without this system, saltwater builds up within the engine and forms a scale that can restrict water flow AND corrode the engine. As water flow is limited, the engine can’t cool down as effectively which can lead to it overheating. This can result in the whole engine having to be replaced.

Freshwater boats use a raw cooling system, whereby the water flows through the water jacket of the engine. Corrosion can still occur over time, as can scaling, but it’s on a slower, smaller scale and is much easier to clean.

When it comes to maintenance, you could use a boat wash for salt water. For example, there are products available that can help to flush the salt out of your engine cooling system.

Salt Water vs. Fresh Water

The real question on everybody’s mind is whether you can use a saltwater boat in freshwater (and vice versa)? The simple answer to both questions is yes, but there are conditions.

Using a freshwater boat in saltwater will require many upgrades. The extent depends largely on the distance from shore you plan to go, and how long you want your boat in the saltwater. As we already discussed, hull design and the engine cooling system will be impacted by the conditions of the sea.

Using a salt water boat for fresh water is a much simpler switch. Your boat shouldn’t need any upgrades as the freshwater will be less corrosive than the saltwater. You would just need to be wary about the depths of the water in relation to the design of the boat.

Got Questions?

Hopefully, you’re now aware of the differences between salt water vs. fresh water boats. Just remember that salt-resistance and salt removal are key features in saltwater vessels.

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