July 31

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Do Jet Skis have propellers ?

By Steve

July 31, 2022


If you are planning to go out jet skiing for the first time, there is a lot of uncertainty about the whole experience. One thing that is for sure is that jet skiing is amazing.

Perhaps you are wondering: Do jet skis have propellers ?

Jet skis do not have propellers that other motor-crafts such as boats and ships have. Instead, it is the jet propulsion engine that aid their movement. This engine has a rotating fan blade whose role is to suck in water used for propulsion. The water is then ejected powerfully from your jet ski engine to produce a thrust.

For beginners, steering a jet ski across water safely is not easy. You need to understand the basics of how a jet ski actually works. To understand how a jet ski is propelled and other common questions, read more.

How do Jet Skis Work ?

The best description of jet skis is that they are a type of motorcycle capable of riding on water. This comparison is based on how the jet ski is driven and how one sits while on it.

However, the main difference between jet skis and motorcycles is in the engine. Motorcycles use the standard combustion engine but when it comes to jet skis, it is a totally different case.

Jet Propulsion System

The uniqueness of jet skis in terms of propulsion is not only between them and motorcycles but also with other sea vessels. Vessels such as ships and boats have drive shafts and propellers but jet skis do not. Instead, jet skis rely on a ‘jet’-just like their name suggests. In a nutshell, jet skis rely on a water propulsion jet system.

Most jet skis have some form of intake system that sucks in water. This water is pulled into the jet ski by a bladed system that operates just like a propeller but not exactly similar. The system is referred to as an impeller-which is the exact opposite of a propeller system.

After being sucked into the engine, water is expelled out at high speeds from the rear end of the jet ski. It is this ejection that propels the jet ski forward. In addition, this propulsion system is also responsible for steering the watercraft considering that the handlebars are also linked to the movable jet.

Speed and Steering

It is important to note that ease of manoeuvrability of your jet ski depends on how fast the motor-craft is moving. The faster you are moving, the easier it becomes to steer your jet ski. This means that at lower speeds, you are less likely to achieve the agility you are looking for when making turns.

How Does a Jet Ski Engine Operate ?

A jet ski engine is very similar to that of a motorcycle or a car. Most jet skis either have a two-stroke or a three-stroke engine. The difference between the two is that while a two stroke engine has up to 3 cylinders, a three-stroke engine has up to 4 cylinders.

Starting a Jet Ski

Starting a jet ski engine uses the same procedure as that of other motor-crafts but this time, the throttle is the feature that sends a signal to the motor to start the engine. A major change regarding how jet skis work is that recent models come with a dedicated key that is required for your jet ski to work effectively.

For your jet ski engine to work, the key should be inserted and kept close by throughout the ride. This recent feature has been helpful in preventing collisions especially because your jet ski will not be able to move for long in the event that you fall off.

Do Jet Skis Have a Cooling System ?

There are two types of cooling systems found in jet skis.

  • Closed-loop system
  • Open-loop system

Closed loop system

The closed-loop system is very similar to how a car engine operates. Typically, the water outside never enters the engine in a closed-loop system. Instead, jet skis with a closed-loop cooling system have an anti-freeze liquid that is used to cool the entire system.

This system comes with a ride plate that is also referred to as a heat exchanger. It is the ride plate that disperses heat from the engine to the water outside. The system works effectively since the water outside is naturally cooler than the engine.

Ride plates in jet skis are very similar to radiators in cars. However, the major difference is that while radiators are cooled by air from outside, ride plates are cooled by water. The reason why the ride plates in a jet ski are found underneath the PWC is so that they are in contact with the water all the time.

This means that when the hot temperature emanating from the anti-freeze liquid exits the engine, it passes through the ride plates and back into the engine for cooling. Under this mechanism, there is absolutely no contact between the engine and the water outside.

Open Loop System

An open-loop cooling system utilizes water to cool the engine. Water is first pulled into the engine where it is circulated before being expelled at the rear end of the watercraft. This is basically in tandem with how jet skis work which is why most traditional jet skis use the open-loop cooling system.

What is the Physics Behind Jet Skis Operations ?

Jet skis can be said to operate using the law of Action and Reaction where every action has an equal opposite reaction. Typically, this is how most jet skis  are propelled and even stopped. The key feature that allows a jet ski to move on water is the impeller. As the impeller rotates, water is sucked into the jet ski and expelled with a high force at the rear end of the jet ski.

With the water jet behind, the jet ski will definitely move in the opposite direction which is forward. The reason why water has to  be expelled at high speed is because jet skis are relatively large objects and at the same time heavy. The more-powerful the jet stream from your jet ski is, the easier it is for you to manoeuvre your motor-craft.

How to Steer Safely on a Jet Ski ?

When riding a jet ski, a good rule of thumb is to exercise caution especially considering how powerful the water jet is. So incredible is the force that it is considered the number one cause of jet ski accidents. If for example a person falls off their jet ski, chances are that they will land in the path of the jet stream.

Such a situation can lead to serious internal injuries since the powerful jet will be slamming into the body of the victim. However, such injuries are not extensive since once you release the throttle, the jet ski will stop moving and so will the powerful jet.

While it is exciting and exhilarating to ride on a jet ski, these crafts are not entirely safe. There are many incidents involving jet skis especially to do with crashes, fires and injuries. In recent times, the risk of incidents involving jet skis has further increased being that modern jet skis can carry up to three riders.

Such risks are the reason why you are required to carry safety equipment during your ride apart from ensuring that your jet ski is insured.

In a nutshell, safety while riding a jet ski starts with taking responsibility before going out on a ride. Remember, jet skis do not have a designated braking system and while riding, the only thing holding you to the machine is the power of your grip.

Final Thoughts

Unlike most watercrafts, jet skis do not have propellers. Instead, jet skis use water to generate thrust that propels them on water. This takes place when the impeller sucks water into the jet ski and expels it through the rear end of the vessel to generate thrust.

Understanding the concept of how jet skis work can come in handy especially in terms of manoeuvrability while you are out riding your jet ski. You are able to understand that it is easier to navigate the vessel while you are at higher speeds than the opposite.

Safety should also be top among your priorities when you are out riding. Riding your jet ski safely requires a little bit of caution, responsibility and knowing your abilities and limits when you are out riding.

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