Perhaps one of the most interesting basis for discussion in the world of watercrafts is the open loop vs. closed loop comparison.

It is basically an argument between Sea-Doo fans on one hand and the owners of WaveRunner and Jet Ski watercrafts on the other side.

Sea-Doo manufactures personal watercrafts (PWC) with the closed loop cooling system while the other two leading manufacturers have the open loop system in their watercrafts.

The rivalries usually take up heat when PWC enthusiasts start to discuss which of the three leading manufacturers makes the best watercrafts. It is not an easy decision to make when you’re outside with little to no knowledge about the three brands.

Therefore, it is important to do your research before taking any sides.

Before buying a watercraft, there are plenty of other things that should be considered as well beyond the cooling system. These factors are typically:

While there are countless different factors that contribute to one company being superior to the others, now we are going to look at just the water cooling systems.


Before diving into which cooling system is the best, let’s look at exactly when the actual advent of air-cooled and water-cooled engines happened.

In the 1968s, Sea-Doo was the first company to have a watercraft that was powered by an air-cooled 320cc engine. (Kawasaki released their first Jet Ski not much later, in 1972).

This engine gave the watercrafts a maximum speed of only 25 mph.

Soon there were multiple complaints of the engine’s inefficiency and overheating so it was replaced in 1969 with a water-cooled 367cc engine.

Shortly afterward, many manufacturers in the industry started using the (open loop) water cooling system and this went on for decades till when in 2002, Sea-Doo introduced their 4-stroke engines that came with the closed loop cooling system.

Ever since then, Sea-Doo is the only manufacturer in the PWC industry that uses a closed loop system while the rest use the open loop systems.

There are, however, older 2-stroke Sea-Doo models available with the open loop systems as well if you look hard enough in the second-hand market.

Let’s watch a short but impressive overview of Sea-Doo’s Closed Loop Cooling System:

The need for a cooling system

Making the decision between which type of cooling system is best can be made easy if we first understand the purpose behind one.

Why do PWCs really need a cooling system?

This is because watercrafts, like all motor vehicles, generate a great amount of heat while running.

Without having an efficient cooling system in place, it won’t take long for an engine to overheat and consequently fail. If your engine overheats and fails, there are a plethora of other damages and problems that come with it.

In order to prevent this from happening in the first place, there is a need for a cooling system in a watercraft.

There are two main types of cooling systems; the air-cooled and the water-cooled.

Air cooling systems, as explained by their name itself, work by cooling down an engine with the use of a fan or simply natural airflow. Airflow systems, however, are not effective with watercrafts or boats.

This is mainly because of the fact that PWCs do not have a large enough surface area to expose their engines to the air.

On the other hand, the water cooling systems use water to cool off the engines and they have been proven to be the most effective in watercrafts.

There are mainly two types of water cooling systems: the open loop and the closed loop.

Open Loop Cooling System

How it works

Open loop cooling systems are the most commonly used water cooling systems in watercrafts by manufacturers.

They use the water that the craft is riding on – the lake or the ocean – and they circulate it all throughout the engine to cool it down.

This is an efficient way to cool down the engines and Yamaha WaveRunners with an open loop cooling system can be seen squirting water out from the back while they are being ridden.

The squirting water while the watercraft is running is perhaps the greatest indicator of how well the cooling system is working.

This method is especially useful in older models that do not have a temperature gauge.

It should also be noted, however, that not every watercraft or boat with an open loop cooling system squirts out the water. This is a feature of only Yamaha WaveRunners, so you won’t find them on other models like Kawasaki Jet Skis.

The reason for this is that Kawasaki Jet Skis – however use open loop cooling system – pump the water directly out into the exhaust system.

The water and the engine exhaust mix together inside the exhaust system and they both exit simultaneously.

Pros of the open loop cooling systems

With the exception of Sea-Doo, all manufacturers in the industry use open loop cooling system and even most of the boat manufacturers utilize this system.

This makes them an easy choice for any new watercraft that you might be looking to buy but you should always know the reasons behind why top manufacturers still use this type of cooling system.

One of the biggest reasons why companies use open loop cooling is that it is an old technology that has been in use for decades. It is fairly simple and has also proven to be highly efficient.

Moreover, it is also effective in the marine environment and does not pose any threat to the ecosystem.

Another major advantage of using open loop cooling systems is that they are easy to service and require less maintenance than a closed loop system.

This is because there are no extra fluids needed to be added to the cooling system which is what makes things quite easier and more convenient for owners.

Additionally, these open loop cooling systems are pretty amazing when it comes to reliability. This combined with their efficient working is what makes open loop systems widely adopted by 99% of the manufacturers in the industry.

Let’s check what Yamaha says about their open loop cooling systems:

Pay attention to these

Surprisingly, the main advantage of open loop cooling is also a disadvantage at the same time.

While using freely available water from the surface below seems like a rational, cost-effective method to cool off a heated engine, there are certain drawbacks to it.

Perhaps the foremost issue lies in the water not being of reliable quality.

If the WaveRunner or Jet Ski is running in a lake, river or the ocean, the water that is taken up to cool the engine might be polluted, contaminated or even simple salt water.

These different conditions of the water that is available to cool off the engine might affect its durability and performance, especially the corrosive brackish water.


In order to prevent extensive damage to the engine, it is recommended for owners to flush the engine of the watercraft with fresh water every once in a while.

For best protection against corrosion from seawater, it is advised to flush the engine with fresh water after every use.

There might be a few cases where owners have never flushed the engines of their watercraft and still enjoyed using them for many years, it is always better to be safe than sorry.

Additionally, one of the arguments against the use of open loop cooling systems is that there is a possibility for debris from the water to be sucked up into the engine causing a potential hazard. Although this is a rare occurrence, it certainly is a possibility and therefore flushing the engine out after every use is highly feasible.

Another potential problem with the open loop system may be due to negligent winterizing of the engine block. When the water temperatures are too low, it expands and the expansion might break the engine parts.

This is why there needs to be extra caution paid to the water in freezing weather.

What you can do to prevent damage to your engine is flush your cooling system with anti-freeze after the season.

It’s essential to do it before freezing weather so it’s wise to do it as a part of your winterizing process. This not only cleans the system but also protects it from the potential damages caused by the expanded water.

Squirting water from Yamaha WaveRunner open loop cooling system

Squirting water from Yamaha WaveRunner open loop cooling system

Sea-Doo Closed Loop Cooling System (CLCS)

How it works

Similar to open loop, closed loop cooling uses surrounding water to cool off the engine.

However, with a closed loop cooling system, the external water never enters the Sea-Doo’s engine.

Instead, a special anti-freeze liquid is used around the inside of a ride plate, which is also known as a heat exchanger, which works to disperse the heat of the engine into the surrounding water.

Since the waterways are much cooler than the engine, the ride plate is able to transfer heat out of the engine and into the water.

The ride plate on your Sea-Doo works similar to the radiator on your car.

However, in your car, the radiator is cooled by air. While the Sea-Doo’s ride plate is cooled by water, they both work in the same way.

They both remove the heat from the system’s closed side and pass it into the external elements (water or air). The anti-freeze liquid is circulated through the engine by running to the heat exchanger.

The heat exchanger is located under the Sea-Doo so it’s in the raw-water continuously. This reduces the temperature on the hot anti-freeze liquid that exits the engine and it is then pumped back to the engine to cool it. Thus, the engine does not meet the external raw-water at all.

For better presentation please see the process on an official video from Sea-Doo:

The pros of Sea-Doo closed loop cooling system

The closed loop cooling system has been in use by manufacturers for a long time as well.

The greatest example is that of a radiator in your car. The length of time and the versatility of use of the system prove that it is, in fact, usable and durable.

Over time, besides Sea-Doo, more and more boat manufacturers have begun supplying closed-loop cooling engines which show us that the trend is slowly but surely evolving.

A major advantage of the closed loop cooling system is that it can be controlled to keep the engine at a proper temperature continuously without relying on the temperature of the water underneath the Sea-Doo.

Moreover, your engine is not susceptible to any corrosion or harm due to corrosive or polluted water, so a closed loop cooling system actually elongates the life of an engine.

It also makes the winterization process easier as raw water never comes near your engine.

Pay attention to these

It is true that the closed loop-system is significantly more complex compared to the open-loop system.

Although these are pretty reliable systems, repairs and maintenances might be more difficult and thus, costly.

Similarly, regular service is also might be more expensive and detailed because it includes the fluids.

Even if you don’t have to flush your cooling system after every ride, it doesn’t mean that you don’t have to do anything after you ride your Sea-Doo.

Let’s take a look at the factory’s recommendation after ride cares:

Moreover, even if the cooling system filled with an anti-freeze liquid, the intercooler and exhaust system are still cooled by raw water.

Because of that, the exhaust and intercooler still need to be flushed with an anti-freeze whenever winterizing.

Finally, the last drawback that is typically pointed out by experts is that the ride plate is easily prone to damage while beaching.

While damages don’t necessarily occur, it is a possibility.

So, you always need to be careful especially if you are beaching regularly.

To reduce the chance of damages, the best practice is to leave your Sea-Doo slightly at a distance from the coast, if possible. You can choose from several good PWC anchors on the market!


When it comes to purchasing a watercraft, the cooling system is mainly not in focus, but it’s definitely a factor.

If we analyze this closely, the open loop cooling vs. closed loop cooling disagreement boils down to the Sea-Doo vs. Waverunner vs. Jet Ski rivalry.

Brand loyalty is strong in many owners, so debates are usually pointless.

Of course, there are pros and cons to each, but at the end of the day, this is not the main point. Both systems are pretty reliable and are in the motorsport industry for decades now.

It’s always essential to do extensive research before purchase and you can make a great start with our watercraft comparison tool.

Beyond the specs and head-by head comparisons, you can find pictures and videos about each model. Don’t hesitate to discover more!

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