Inboard Vs. Outboard Motor: What Are the Differences, and Which is Better?

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Last Updated on March 19, 2025 by Paul Clayton

Inboard Vs. Outboard Motor: What Are the Differences, and Which is Better?

Are you a boat owner or a boat enthusiast? Understanding the differences between inboard and outboard motors is crucial. These two types of engines each have unique advantages and disadvantages that can significantly impact the performance, maintenance, and overall boating experience.

• Positioning: Inboard inside and outboard outside affect balance, storage, and maintenance.
• Propulsion: Inboard propels via a drive shaft. Outboard is a self-contained unit with an engine and propeller.
• Steering: Outboard pivots engine for thrust. Inboard uses a rudder behind the propeller.
• Maintenance: Outboard accessible for repairs. Inboard challenging due to limited space inside the boat.
• Fuel Efficiency: Outboard more fuel-efficient tech advancements to enhance efficiency.
• Performance: Inboard offers more speed and power. Outboard tech advancements narrow the gap significantly.
• Noise and Vibration: The inboard is quieter, with less vibration for a smoother ride.

When it comes to boats, there are a lot of technical things you have to look into. From the size of the boat to the best fishing spots, opinions can vary greatly.

Inboard vs outboard motor is a frequent debate among the boater community. So, what are the differences between the inboard and outboard motors? 

You don’t need an engineering degree to know which is better. If you know the pros and cons of each type, you can better judge which one is more suited for you.

After all, when it comes to boats, technical details aside, you have to listen to your gut. 

But before you listen to your gut, let’s examine why this choice is so important and what each offers.

Understanding Boat Motors

You will get multiple answers if you walk down your local watering hole and ask some boat owners the same question. Their answers, even though conflicted, are not all wrong.

There is no easy answer to whether the inboard motor is better than the outboard. 

Boats use engines or motors to run. Motors are powered by electricity, whereas engines are powered by fuel. Determining whether a boat is equipped with a motor or an engine can sometimes be confusing.

This is because boaters often use the terms interchangeably.

The motor is what moves the boat on the water. So you can guess how important a motor is for a boat. It’s just like your car’s engine, except it is designed to be suitable for marine conditions.  

When buying a boat, you can start by finding the correct motor size that will allow you to maximize your boat’s performance.

Furthermore, the engine’s weight and horsepower hold the same level of importance. Hence, deciding on the motor’s make, type, and manufacturer will be necessary.  

Inboard Motors

An inboard motor or engine is the one located inside the boat. Just as your car engine moves the wheels, the inboard motor moves a different wheel type. This is the propeller that runs the boat. 

The motor has a power head that is attached to a drive shaft. This shaft is essentially part of a drive system that runs the propeller. The propeller can drive the motor forward or backward. The boat’s operator uses the drive system to control the boat. 

This motor is bolted in the boat’s middle or back. Since it’s on the boat, hence the name inboard motor. Even within the inboard category, you can choose from different types. 

We must look at the different types to better compare it with the outboard engine.

Types of Inboard Motors

The distinguishing part between the different inboard motors is the drive system. Even though boaters use the general term inboard motor for virtually all of them, they perform pretty differently. 

Here are the three types of inboard boat motors:

1. True Inboard

The True Inboard motor or engine uses two types of drive systems. When we say the system, we mean the drive shaft, propeller, and engine, all included. So, the two drive systems are D-Drive (Direct Drive) and V-Drive.

In the D-Drive, the engine is in the middle of the boat. The shaft is coming out of the back of the engine. It uses a transmission system that engages the rod into the water, with the propeller at the end of it. 

The V-Drive is the true inboard placed on the back of the boat. The difference is that the shaft is coming out of the front of the engine.

The transmission on this has a V-shape, with the other end of the shaft heading out at the bottom of the boat. The propeller is at the end of the shaft. 

The transmission is inside the boat in both the drive systems. The rudder behind the propeller changes the direction of the ship. 

2. Inboard/Outboard (I/O) or Sterndrives

This type of inboard engine is placed at the back of the boat. The drive system on Sterndrive goes through the transom of the boat. This system consists of two parts: the upper and lower units. 

These two units are essentially the transmission of the engine. The upper unit changes the spinning motion from vertical to horizontal.

This spinning motion goes to the lower unit, and the unit spins the propeller in a clockwise or counterclockwise rotation. 

What makes this system different is that it does not have a rudder. Since the entire drive system can turn left or right, there is no need for a rudder.

Additionally, it can trim the drive system up. As a result, more of the boat is above water, which allows for higher speed. 

You can read more about the differences here. 

3. Jet Drive

This is entirely different from the other two types. However, it’s still a type of inboard engine because it’s found inside the boat. It uses water from under the boat and an impeller to create a jet. 

When the water comes out forcibly, it pushes the boat. It’s basically how a jet ski operates. The principle is followed on a boat, much bigger than a jet ski. 

This type of system is not as common as the other two. However, it’s gradually making its way thanks to technological advancements. It can deliver relatively high speeds for a lightweight boat. However, it does utilize a lot of power. 

Pros & Cons of Inboard Motor

To make it easier for you to understand the inboard motor, here is a detailed look into the limitations and benefits it offers.

Pros:

The most significant advantage of an inboard engine is its drive system. The engine is hidden, protecting it from moisture, dust, and water.

Since it’s hidden, it does not show, and the boat’s overall appearance is much cleaner.

Inboard motors are generally high-quality and, therefore, long-lasting. These engines use diesel, which has a longer life. On sailboats, a diesel engine can run for up to 30 years. This is why these are more expensive, too. 

The boat is more stable, with the engine inside and in the middle. You do not have to worry about losing the balance of the boat. In smaller boats with the engine on the outside, balance can be a problem for a beginner. 

Cons:

A boat with an inboard motor will cost. However, the maintenance is low, so it will not cost you much money. 

Another disadvantage of an inboard motor is that it requires space on the boat. This leaves little room for the interior of the boat. This is not such a significant problem with bigger boats, but space can be an issue with smaller boats. 

Lastly, repairing these can be a nightmare. Since the engine is hidden in the hull, cutting through it is a hassle. Even when you get to it, there is little room to work on it. 

Outboard Motors

Outboard motors are bolted to the boat’s transom and located entirely on the boat’s exterior. They are a self-contained package containing everything, including the engine, propeller, cooling system, and gearcase. 

The powerhead is at the top section, while the middle section attaches to the boat. The lower section is the drive system. Two-stroke engines are the most common for outboard boats. These use oil for lubrication as well as fuel.

Many newer boats use a four-stroke design—even the ones with two-stroke use direct injection, which is cleaner in fuel burning. You steer the outboard boat with a tiller or a steering wheel that makes the entire engine swivel. 

Outboard motors are a huge market. These are generally more popular for fishing and recreational boats. It’s a lot easier to handle. Replacing it is also more accessible as it’s on the boat’s exterior. 

Pros & Cons of Outboard Motor

Here is a quick look into the pros and cons associated with an outboard motor.

Pros:

An outboard motor’s small size and portability make it ideal for some boats. You can easily remove it when it’s time for repairs and tilt the entire engine to maneuver the boat. 

You can trim the boat up so it does not hit the bottom of the water. So this makes this motor ideal for saltwater. 

It can also deliver good speed, especially for a small boat. Since it’s on the boat’s exterior, you have more space on the inside. 

Its main advantage is its low cost. Even though you will have to replace it sooner, the overall cost would not be so high. 

Cons:

The disadvantage of an outboard motor is that it is visible. If you’re all about the boat’s looks, an engine stuck outside the boat is not the most appealing look. 

Also, there are some safety hazards. If the fuel tank is not placed correctly, it can prove dangerous. Similarly, if the engine size does not fit well with the boat’s weight, it can become unbalanced and tip over.   

This kind of boat engine does not have a high power-to-weight ratio. Simply put, it does not have enough torque to withstand a lot of cargo. You can add more motors, but that will be a lot of work, not to mention additional costs. 

Inboard Vs. Outboard Motor: Comparison

Now you know what each type of motor is and its pros and cons. It’s time to compare the two directly. This will help you reach the two kinds of engines in different aspects. It will boil down to your own boating needs. 

• Cost

Inboard motors are way more costly than outboard motors. The one-time purchasing cost for outboard engines is low. However, maintenance and replacement costs are incurred. 

An inboard motor can give you 1500 hours, while an outboard motor will give you 750-900 hours. After these hours, you will have to complete the required maintenance for the engine.

Inboard motors generally last longer, so you will not have to replace one anytime soon. 

You should also factor in insurance costs. Since inboard motors are more expensive, their insurance is costlier, too. 

• Maintenance

Aside from the one-time buying cost, it would be best to consider maintenance costs. Generally, inboard motors have higher maintenance costs as compared with outboard motors.

However, the low frequency of maintenance or repairs offsets this cost.

Sterndrives are the most expensive to fix as the engine is placed in an enclosed space. Outboard motors may be cheaper to repair and maintain, but they do not have a life as long as their inboard counterparts.

You can do minor repairs by yourself to save money.

Inboard boats are also susceptible to issues because of their positioning. They can be difficult to open because of a small hatch in the housing. Once you open, water and moisture can cause damage. 

• Water Activity  

The water terrain you take your boat on influences the life of your boat. Saltwater is corrosive for most materials present in the boat and engine. However, you can prevent it by trimming the engine off the water.

The outboard wins the race here, as it is easy to maintain and trim. An inboard system is left in the water for the corrosion to grow. Even though the hull protects the engine, it eventually needs repair, which is expensive for inboards. 

• Safety

When it comes to safety, the discussion is relatively straightforward. The design of inboards makes them safer than outboards. As the fuel tank is secured inside the hull, it’s less likely to get damaged, leak, or burst.

However, if you design the boat better, you can prevent this from happening in an outboard.  

• Fuel Economy

Today’s boat engines are much more efficient in fuel consumption. With climate change becoming a significant threat, companies are moving towards even better engines that produce less carbon footprint.

This essentially requires less fuel usage. 

If we compare numbers, the outboard motors offer a better fuel economy. This is simply an advantage because of their low weight and faster speeds. But in terms of weight-to-power ratio, the inboard comes out on top. 

Fuel economy is subjective and may vary by the particular motor model, whether it’s inboard or outboard.

Generally, the older the motor, the higher its fuel consumption. Also, if a lot of weight is on board, it will consume more fuel. 

• Power

Inboard motors’ directional thrust and integral skeg make them easy to maneuver at low speeds. As a result, it’s easier to dock such boats. The opposite is the case with outboard motors. 

The outboard motor needs thrust to steer. So it would be best if you had more power to maneuver it. But more power is not ideal when you have a small boat. 

Which One Should You Choose?

If you’re confused about whether to go for an inboard or outboard motor, evaluate your purpose. You can weigh the pros of each against one another in the context of your boating needs. 

The inboard motor may have more pros, but in some cases, the outboard motor is better. For smaller boats, the outboard motor is better.

It can deliver the speed you need. It will keep the engine out of water when you trim it. Also, it will not cost you a fortune. 

For bigger boats that you use pretty often, especially if using commercially, an indoor motor would be the right choice. It will deliver the performance you need.

Also, you can put more cargo and people on the board. Most importantly, it would not wear down so quickly. 

Most experts say that inboard motors are more reliable. However, that is changing now. Outboard motor manufacturers are producing high-quality motors that are cutting in close in terms of reliability.

Yes, you will make repairs often, but the motor will last longer.

Another important and perhaps deciding consideration is your budget. Are you a severe boater who does not have any budget restrictions?

Are you an occasional angler who does not have a big budget? This should help you make a decision, too. 

In case you didn’t know, you can also convert an inboard into an outboard. You will need to hire a professional to do that for you. 

How Long Do Outboards Last?

The lifespan of outboard motors is a concern for many boat owners, often questioning, “How long do outboards last?” An outboard motor sustains for around 1,500 hours or approximately 7 to 8 years.

However, it’s crucial to note that this lifespan can vary significantly based on the motor’s make, model, and how it’s maintained. Regular servicing and proper care can extend the longevity of the engine significantly.

Thus, how long outboards last largely depends on the care and maintenance invested in them, potentially enabling them to last well beyond the average lifespan.

Final Words

The comparison between inboard vs. outboard motors is an exciting topic that attracts boat enthusiasts worldwide. In terms of positioning, an inboard motor is located inside the boat’s hull, while an outboard motor is attached externally.

This positioning impacts the boat’s balance, storage capacity, and maintenance requirements. The propulsion method also varies; an inboard motor propels the boat via a drive shaft, whereas an outboard motor is a self-contained unit with its engine and propeller.

In terms of steering, an outboard motor pivots the entire engine for thrust direction control, while an inboard motor uses a rudder placed behind the propeller for steering.

Maintenance accessibility is another crucial difference; outboard motors are more accessible and easier to repair due to their external positioning, whereas inboards present a challenging task due to the limited space inside the boat.

Fuel efficiency is another area where differences are evident. Outboard motors are traditionally more fuel-efficient, and their efficiency has only increased with technological advancements.

The choice between the two should depend on individual requirements, including the intended use of the boat, maintenance capabilities, and fuel efficiency needs.

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