Saltwater vs. Freshwater Boats: What’s The Difference?

can you use a freshwater boat in saltwater?

What’s The Difference Between Freshwater and Saltwater Boats?

While many boaters find they tend to stay close to their main body of water (lake, river, etc.), there are times where freshwater boaters may have the opportunity to take their boat to the coast and use it in salty water. This brings up the big question of, can you use a freshwater boat in saltwater. It has been many years since I was a freshwater boater pulling skiers and tubers. Over the past decade, my passion has been saltwater boating. For this reason, I had to do a little research to answer the question for today’s boats.

Can You Use A Freshwater Boat In Saltwater?

So, can you use a freshwater boat in saltwater? Yes! Most boats are capable of being used in both fresh and saltwater, but some boats may require modification before use in saltwater. Any boat used in Saltwater will require a thorough rinse and flush with fresh water to preserve and protect the boat. It is important to know that saltwater can wear out boat components quicker than freshwater use.

In this article, we will discuss the differences between freshwater and saltwater boats. We will also discuss common issues and what to be aware of if you do take your freshwater boat in the salty water. Not all boats and boat components are well suited for saltwater use.

Quick Disclaimer: While I did a lot of research for this article, I cannot know all of the details for every boat ever built. For this reason, I suggest checking your owners manual or with the manufacturer of your specific brand of the boat to be safe.

If you have been boating on lakes for many years, you probably have your maintenance routine well rehearsed. If you are just thinking about or have recently started taking your freshwater boat in salt water, you need to add several items to your boat maintenance list.

Let me be clear! Any boat regardless of how its propelled (inboard/outboard (I/O), jet boat, outboard, etc.) cannot withstand the long-term corrosive effects of saltwater. Every boat engine needs preventative maintenance to address exposure to saltwater and its corrosive nature.

Here are a few things to consider if you are thinking about taking your freshwater boat into saltwater…

What Does Saltwater Do To Your Freshwater Inboard/Outboard?

A lot has changed over the years with inboard/outboard (I/O) driven boats. One thing that has not changed about I/O powered boats is that I/O engines are raw water cooled. This means that as you run your boat and the engine gets hot it sucks water from the outside of your boat and runs in through the engine and back out of the boat as a way to cool off your boat’s engine.

You can probably start to see why this can be a problem in saltwater. In freshwater lakes and rivers, your I/O sucks in raw freshwater, it cools off the engine and gets spit back out. This is fine with fresh water, but salt water getting run through an engine can be damaging to an engine if it is not thoroughly flushed with fresh water after every use.

A true saltwater marine engine that is I/O will have a closed system with a heat exchanger to cool off the engine.

What Is A Closed Cooling System With Heat Exchanger?

A closed cooling system is a closed loop cooling system that allows an inboard/outboard (I/O) engine to operate in saltwater while still using treated freshwater to cool the engine. The closed freshwater circuit can be thermostatically controlled so that the engine operates at its designed temperature.

How Does A Closed Cooling System Work?

Typically, there is a small tank on the top of the engine that uses a mixture of both freshwater and coolant. This freshwater mix is circulated through the engine and through a heat exchanger. Heat from the engine is absorbed by the water in the system. Since the freshwater is now hot from the engine, raw water is pulled in through the seacock, but it only flows through the heat exchanger jacket. When the cooler raw water goes into the exchanger, heat is transferred from the freshwater to the raw saltwater through the heat exchanger jacket. The two types of water never touch, but it allows the hot water to get pumped out of the boat and keeps the I/O engine running at its proper operating temperature.

If I Use An Inboard/Outboard or Sterndrive Boat In Saltwater What Should I Do To Make It Last?

Flush, Flush, Flush the engine with fresh water after every use. No exceptions! I know this sounds extreme but even I/O boats designed for saltwater have rust and corrosion issues. The best thing you can do to extend the life of your I/O boat is to flush it with fresh water for five to ten minutes or more at the end of the day.

Note: It is important to flush all boat engines with freshwater at the end of the day, not just I/O’s but outboards should be flushed too.

I still remember going out offshore fishing with my wife’s Grandfather. He had a 24′ Albemarle that he would take offshore and nearshore fishing just about every morning. It was a great rough water boat with its deep-v design, but having an I/O for power made for a lot of extra maintenance. Thankfully, he was a bit of a McGyvor type (I think that is the nice way to put it) and he rigged up a freshwater flushing system with pipes and a five-gallon bucket.

When we got back to the dock after a day of fishing, he would flip a valve, fill up a five-gallon bucket of water from a water hose and use that to flush the engine with fresh water. I do not know many boat owners who would have the knowledge of how to build such a system, nor would many people today be willing to do that since today, outboard engines are built to handle the harsh saltwater environment.

Another important point to consider is that sterndrives often do not tilt out of the water. If your boat is not on a lift or stored on a trailer, the lower unit (outdrive) typically sits in saltwater. As a result, you need to continually check and replace your boat anodes.

You also should thoroughly spray and flush the drive part of the engine according to manufacturer instructions.

If your sterndrive boat is kept on a trailer, you can attach a garden hose to muffs and flush the engine on the trailer similar to how you flush an outboard engine. On your inboard/outboard boat, regardless of how much you flush and clean components, just know you will have to replace parts like water pumps and manifolds more often.

An I/O manifold may last ten to twelve years when used in freshwater, but in saltwater, you may only get a few seasons out of a manifold. I have heard of people having to replace their manifolds after just three years of saltwater boat use.

What Is An Anode On A Boat and What Does It Do?

In simple terms, an anode is a piece of metal on your boat that deteriorates faster than other metals and it is used to protect those other metals from corrosion and failure.

In freshwater, boats often use magnesium anodes, but these will need to be used for long-term saltwater use. If you can find aluminum anodes they would be a good choice, but if not zinc anodes are good for saltwater use too. In freshwater, checking your anodes are somewhat of an afterthought, but in saltwater, routinely checking your anodes is a key part of preventative maintenance. Anodes should be replaced when they are more than half wasted.

Outboard Boat Motors Used In Saltwater

So you have an outboard engine on your boat… congratulations! This is the easiest engine to transition to saltwater usage. However, just because it is the easiest does not mean it is the same as using an outboard on a lake. When you use an outboard engine in salty water, you must be religious about flushing the unit with freshwater everytime you get back to the dock. Yes, I really do mean EVERY TIME!

How To Flush an Outboard Motor in the Water

It is time to flush the salt water out of your outboard engine. Most modern outboard engines come equipped with built-in garden hose attachments. This makes the task of flushing your engine easy and there is no excuse for not flushing the engine. If your engine does not have this feature you can get one of these to do the job. Amazon LinkOpens in a new tab.

Using the freshwater at the dock, with the engine off and trimmed out of the water, simply run water through the engine. In general, you will want to flush the engine for 5 to 10 minutes

This is the easiest engine to transition to salt. But you’ll now have to religiously flush the unit with freshwater when getting back to the docks. Every ime. Modern outboards come with built-in garden-hose attachments, making the job a cinch. Using freshwater at the dock, with the engine off and trimmed out of the water, simply run water through the engine. The rule of thumb is for five to 10 minutes, but you should consult your manual or a qualified outboard mechanic.

Additive products such as CRC Salt Terminator, which cleans internals and inhibits corrosion, can further add to peace of mind. For trailer boats without garden-hose attachments, use ear muffs (or flush muffs) attached to a running hose once the boat is out of the water. With muffs, the engine must be started to flush properly. Check your manufacturer’s instruction before flushing.

Here Are A Few Other Popular Topics To Consider When Using A Freshwater Boat in Saltwater

Electrical Wiring and Hardware Components In Saltwater – While automotive grade wiring and hardware are popular for use in freshwater environments, they will not last long in the harsh coastal environment. The corrosion can quickly lead to ugly brown rust stains from mounting screws and fasteners. Don’t be cheap with your wiring and hardware. Be sure to buy marine-grade quality components. Yes, they are more expensive but well worth the money when in a saltwater environment.

Tip: Keep Your Bilge Dry – Salt sitting in the bilge of your boat is much more damaging that freshwater sitting in the bilge. One specific area to check is the wiring connections on the bilge pump. These frequently corrode quickly and you may need to reseal or replace them.

Do You Need Bottom Paint To Use A Freshwater Boat In Saltwater? – Many coastal boaters will use anti-fouling paint on the bottom of their boat hull to keep barnacles and other organisms from growing on the bottom of their boats. This antifouling paint is often called “bottom paint”. For most people, bottom paint is not required if you will only keep your boat in saltwater conditions for two or three days in a row. However, if you will be storing your boat in the water full-time you will definitely need bottom paint.

Don’t Forget To Protect and Clean Your Trailer – Yes, your boat will spend more time in the saltwater than your trailer, but trailers are negatively impacted by exposure to saltwater too. Give your boat trailer the same freshwater wash down as you give your boat.

Boat-trailer frames are typically constructed of galvanized steel or aluminum, with the aluminum being far more resistant to saltwater corrosion.

In addition to the trailer frame, your trailer brakes and hardware need to be protected and flushed with fresh water too. Drum brakes are inexpensive and are often used on trailers. The downside to drum brakes in saltwater conditions is they easily trap salt water in them when launching or retrieving your boat. There are special drum brake flush kits you can get if you need them. Here is an example of a drum brake flush kit. Amazon LinkOpens in a new tab.

Kern Campbell

Kern is a life long boater who finds great happiness sitting at the helm of a boat running on the open water. When he's not running the boat, he's likely anchored up along the beach with his wife, kids and good friends enjoying a great day at the coast.

Recent Content