Thinking of getting a jet boat? While not the most popular type of boat out there, jet boats have many advantages.
Jet boats are better for shallow waters than propeller boats, and they are also easy to maneuver at high speeds. At low speeds, though, they are less maneuverable, and they also wear out quicker and make a lot of noise.
What exactly are jet boats, though, and how do they work? For which situations are jet boats most suitable, and do the potential drawbacks outweigh the advantages?
In this article, we will discuss all that and more, so read on.
What Are Jet Boats, and How Do They Work?
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A jet boat, also called a water jet boat, is a type of boat that propels itself via a jet stream of water ejected out of the back. What makes jet boats unique is that there are no propellers on the outside of the craft.
The boat uses a pump to pump water into the craft from the ocean or river. It uses an impeller, which is a rotating device that helps channel the water through the system, from the ocean into the craft and back into the ocean via a nozzle on the back of the craft.
There are also stators, also called stages, which increase the velocity of the water flow. While most jet boats have just one stator, some might have two or three.
The jet stream that comes out of the nozzle in the stern is what propels the boat forward, and repositioning the jet stream allows the navigator to change direction.
Getting into the physics of why this works is beyond the scope of this article. In short, it relies on Newton’s third law of motion – that every force has an opposite reaction.
When there are two opposing forces, if A exerts pressure on B, B will exert an equal amount of opposite pressure on A. So, a jet stream exerting pressure on the water will cause the water to exert an equal amount of pressure back on the boat, causing it to move forward.
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Jet boats were invented in the 1950s by an engineer from New Zealand called Sir William Hamilton. His goal was to design a craft that can operate in the shallow waters of the New Zealand rivers (more on why jet boats are perfect for shallow waters later).
While various people did try their hands at inventing jet boats earlier, those models generally were not successful and did not catch on in popularity. They were often low quality, didn’t have many advantages over regular propeller boats, and were just inefficient.
One of the biggest discoveries of Sir Hamilton was to expel the jet stream above the waterline. If you’ve ever seen a personal watercraft that uses a jet system, you might have seen a noticeable jet stream coming out of the back.
This is a bit counterintuitive, but it actually makes no difference whether the nozzle is located above or below the waterline in terms of performance. In fact, placing it above the waterline means that the craft will have an easier time in shallow waters, as there will be nothing protruding below.
Water jet boats are often small, but large jet boats exist as well. In general, the technology is perfect for high speed vessels, such as patrol boats, and vessels that need to operate in shallow waters.
However, there are some pretty large water jet boats as well. For example, there are passenger and car ferries that are propelled by water jets; there are also various military vessels that employ this system, such as littoral combat ships of the US Navy.
Jet Boats vs Regular Propeller Boats
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Standard propeller boats have a propeller on the outside of the boat. This propeller rotates within the water under the hull of the vessel and pushes a mass of water backward.
An impeller also rotates, like a propeller, but its goal is simply to pull water in through the jet stream system, as I mentioned above. The actual propulsion and forward motion of the craft is caused by the jet stream streaming out of the nozzle in the back, due to Newton’s third law of motion.
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The main difference, at the end of the day, is that jet boats do not have an external propeller like regular propeller boats. This external propeller makes propeller boats unsuitable for shallow waters, as the propeller might hit the ground under the water or hit rocks.
You can also back a jet boat up to a shore, as there is no propeller that might get in the way.
While you can reverse a propeller boat by changing the direction of the propeller, reversing a jet boat is accomplished by using a deflector to change the direction of the jet stream. That’s similar to how you turn a jet boat – by changing the direction of the nozzle or by using deflectors to change the direction.
Jet Boats vs Other Types of Boats
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Not all boats use propellers or jet streams. In fact, many boats have no motor at all.
Most kayaks and canoes, for example, are propelled forward via manual paddling. Some kayaks or canoes have foot pedal systems that allow you to do most of the work with your feet, conserving energy.
Sailboats, meanwhile, make use of the wind to propel the boat forward.
Pros of Jet Boats
Let’s get into the advantages of jet boats before we take a look at some of the disadvantages. Here are the top reasons to use a jet boat.
1. Great for Shallow Waters
The first advantage of jet boats is that they are very operable in shallow waters – since there are no protruding elements, you only need a few inches of clearance.
Another thing – since there is nothing sticking out under the vessel, jet boats typically have less drag.
2. Quick Stopping
Another big advantage of jet boats is that they are so easy to stop, especially when you need to make a quick emergency stop.
This is known as the crash stop, which allows you to completely stop your vessel in as little as the length of the same vessel.
Remember what I said about reversing a jet boat? You use a deflector to change the direction of the stream as it exits the vessel.
By deploying this deflector and reversing the flow of water, you will stop the vessel immediately.
To stop a propeller boat in the quickest amount of time possible, on the other hand, you would need to reverse the direction of the propeller, which takes more time.
3. Faster Acceleration and Easy to Maneuver
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Jet boats are also known for their great maneuverability. You can accelerate quickly as well.
One maneuver that you can do on a jet boat is quickly spinning it around. To do that, you cut the throttle of the engine, turn the steering as fast as possible, and then turn the throttle on again to reverse direction and spin the boat around.
In a kayak, you might need to use reverse paddling, a technique that not everyone knows.
The fact that there is no drag also makes them very nimble. The absence of a rudder or propeller gripping the water means you can make a 180 degree spin rather quickly.
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4. Safety
There’s definitely something to be said about the safety of jet boats compared to prop boats. Without a propeller sticking out, you don’t have to worry as much about potentially injuring someone, such as a swimmer.
If you are going with kids, that might be a big deal for you. Jet boats can give you added peace of mind.
Cons of Jet Boats
There are several disadvantages of jet boats as well. Here are some things that you might not like about jet boats.
1. Not Very Durable
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Jet boats use a high RPM to turn the impeller. This means that the engine will wear down a lot quicker than you might expect.
Durability is an issue with jet boats – you might find yourself replacing worn out parts sooner rather than later.
2. Low Fuel Economy
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Similarly, jet boats have a low fuel economy. It uses up fuel rather quickly, mainly due to the higher RPMs they require to operate efficiently.
Thus, over the long run, you might find yourself spending a lot of money on fuel.
3. Noisy
Jet boats are incredibly noisy! Compared to standard modern propeller boats, jet boats make quite a ruckus.
You may be able to install insulation on the engine compartment to reduce the noise levels somewhat, but it’s only effective up to a point. The increased noise is due to the higher RPMs of the engine.
4. Can Get Clogged
The impeller draws water in from the ocean or lake into the boat. However, together with water, various foreign objects can get drawn in as well, such as debris, dirt, mud, and even rocks.
There is usually a grate at the opening that will catch a lot of the debris. However, smaller debris can get in and clog the system, damaging the impeller.
Most jet boats provide access from inside the boat so you can clean the grate.
It is particularly a concern with jet boats because they are often used in shallow waters, sometimes just a few inches above the waterbed, which means that they are exposed to more floating debris such as sand, paper, and mud.
5. Not Good for Low Speeds
Jet boats just aren’t as good at low speeds. They are highly maneuverable at high speeds, but at low speeds, they are not.
Remember, to turn a jet boat, you rely on changing the direction of the jet stream. When it’s not that strong, turning the vessel will be more difficult.
Jet boats are even worse at low speeds when reversing them. Astern movement relies on deflecting the direction of the water, as I mentioned.
While that works well at high speeds, at low speeds it can be quite tricky.
Jet boats are also often less stable due to the absence of a rudder. While no rudder hanging down means that it’s great for shallow waters, docking it can sometimes be tough.
6. You Will Lose Horsepower
In general, you can expect an engine on a jet boat to be around 30% less efficient than a similar-sized engine on a propeller boat. Many people refer to this as jet boats “losing horsepower.”
If you are accustomed to certain speeds on your propeller boat, you might be expecting the same speeds when buying a jet boat with a similar engine. I’m here to tell you that there’s a good chance it will be quite slower, as the engine has to do a lot more work pulling water in and pushing it out.
Are Jet Boats Easy to Maintain?
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When it comes to maintenance, jet boats are somewhat strange. On the one hand, they often require less maintenance than propeller boats due to the absence of an outdrive.
While you do need to occasionally clean the boat from any sediment and debris the impeller brought in, overall, it is lower maintenance than propeller boats. Cleaning the grate doesn’t usually take a long time; you can use a garden rake to reach the grate and clean it in between trips.
On the other hand, they can also be expensive to maintain and repair.
The simple reason for that is that jet boats are less common. They’re not as easy to find and they are just not as popular.
Therefore, finding parts is a bit more difficult, as is finding specialists who know how to maintain and repair these boats. They frequently charge more.
With inboard jet drives, you also don’t need to grease the drive bearing. If you have an aftermarket outboard jet drive attached to your boat, though, you will need to grease it every 10 hours or so, and you’ll need to purge it every 35 hours or so.
In other words, you’ll be greasing it before every trip, more or less. That is a significant maintenance task that can be really annoying.
With any jet boat, though, you will still need to do yearly maintenance, so make sure to follow the maintenance advice from the manufacturer.
What Are Outboard Jet Motors?
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In this article, I’ve mostly been talking about inboard jet boats – a boat that has an inner system without an external propeller. However, I also mentioned that there are outboard jet boat motors.
These are aftermarket outboard jet systems that you can use to convert a typical outboard boat to a jet boat.
You will get a kit that you can install on your prop boat, complete with an impeller. It will draw in water from the river or lake and shoot it out in a jet stream to propel the boat forward, just as with a regular jet boat.
The main difference is that it will be an external system.
There won’t be an impeller sticking out of the boat, but the jet drive is an external aftermarket part. There will be an intake on the bottom of the kit, drawing water in from the ocean.
Outboard Jets is by far the most popular company making these systems. The company manufactures over 80 models for different boats, so check your motor make, model, horsepower, etc. to find the right model for you.
Should You Bother Getting a Jet Boat?
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Jet boats are usually purchased for specific applications, particularly shallow water. For river running, they are great.
If your plan is to use your boat in the ocean, it probably isn’t necessary. You can still use it, but most people would just opt for a standard prop boat.
It’s not that jet boats are necessarily more expensive; there’s just a smaller selection of them available. Sure, there are always plenty of options online, but you might want to run your boat for a test drive before buying it to get a feel for it.
Yamaha is well known for its jet boats, though, so if you have a Yamaha dealer near you, you might want to give them a call and find out whether they have any jet boats available.
Jet boats are also good for doing tricks due to how maneuverable and nimble they are.
It might be helpful to think of a jet boat like a superbike. Super bikes are motorcycles that operate extremely well at high speeds, and you can do lots of stunts with them.
When it comes to slow riding in traffic, though, super bikes aren’t that great. The speed is just too much.
Similarly, jet boats are great for speeds and feeling in control. They give you that sports car or sports bike feeling, but at low speeds, they can be quite choppy.
So, know what you want before deciding which boat to get. If you do very little shallow water boating, it might not be worth it.
If you have a friend who owns a jet boat, you could ask them to let you try the boat so you get a feel for jet boats.
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You might also opt for a Jet Ski, a type of personal watercraft and jet boat in which the rider sits or stands on top of the boat, not inside it. They are mostly used for fun and recreation.
Wrapping It Up
While jet boats have many advantages, such as quicker stopping and nimbleness, they tend to be less efficient than regular propeller boats in terms of horsepower and fuel economy.
Jet boats are best for shallow rivers because there is no propeller jutting out of the boat, thus requiring little clearance to operate. They are also great for recreation – Jet Skis being great examples.
However, they are less popular than prop boats and harder to find. Repairing and maintaining them might also be a bit more difficult, as you would need to find a specialist who knows how to deal with jet boats.
