What to Consider When Buying a Boat Motor

Like if this guide is helpful
What to Consider When Buying a Boat Motor

All modern boats, even those designed for wind propulsion like sailboats, use a motor. Whether the motor is the principal method of moving the boat, or used only as a backup system, it has an important job to do. If the motor breaks, the boat becomes stranded. Therefore, choosing the correct motor based on its style, size, and power ultimately affects how well the boat handles in the water. This is easier said than done, as a quick trip to a boat shop, or browsing through an online listing on eBay, easily results in hundreds of popular options.

Therefore, the first step when it comes to buying a boat motor, is to do a little bit of research beforehand into the different types. Be sure to also discover how they are used on various boats. Understanding how the engines work, and how they provide power and consume fuel can help even a first-time boat owner make an intelligent buying decision.

Motor Terms

Before getting into a discussion about boat engines, it is helpful to understand some key terms. Horsepower is the measure of power an engine has. The higher the horsepower, the stronger it is. Torque is the amount of turning power that an engine has. Motors with a high amount of torque tend to accelerate quicker than those that do not.

Motor Styles

A few generations ago, customers were limited in the different motors available for their boat. It was either an outboard carbureted 2-stroke motor, or nothing at all. Today's engines are a little more complex, but they are far more versatile.

2-Stroke Outboard Motor

2-Stroke outboard motors continue to be popular, and the newest models are a great improvement over the old design. These motors used to garner a bad reputation as noisy gas guzzlers, but environmental regulations caused manufacturers to create lighter, more fuel efficient models. They are powerful motors, and the largest are strong enough to work on medium offshore boats. However, they are commonly found on flat-bottom and fishing boats.

A downside to the 2-stroke engine is that it needs both oil and gasoline to run. Also, because it works twice as fast as a 4-stroke engine, it gains power but loses in longevity. Old carbureted 2-stroke engines still lag far behind in terms of fuel efficiency, making them costly engines to use.

4-Stroke Outboard Motor

4-Stroke outboard motors use an internal combustion engine that is more similar to one found in an automobile as opposed to a 2-stroke engine. This means that operators only have to add gasoline to the engine since it uses an oil filter. They last longer than 2-stroke engines and produce less pollution than the older models.

However, 4-stroke motors lack the horsepower and torque offered up by comparable 2-stroke engines. This means they are less versatile for boating. It is best to use a 4-stroke engine on a small inland boat that does not venture into the ocean. They are commonly found as backup motors for sailboats and the main engine for inland fishing boats.

Gas Inboard Engines

An inboard gas engine sits inside the boat, unlike an outboard motor that hangs onto the back. The engine is often in the centre of the boat with a drive system that turns the propeller while an exhaust pipe transfers fumes out through the stern. These engines are quiet for their size and usually have low running costs.

They are larger and heavier than outboard motors, but they are also stronger. Some models come with up to 1000 hp, enough for towing boats and large yachts alike. A downside to this is that gas engines have no means to trim the propeller.

Diesel Inboard Engines

Diesel engines are similar to gas engines, except that they use diesel fuel instead of gas. The engine is slightly more complex than a gas engine as well, but this leads to its long life expectancy. No other motor can match the lifetime of a diesel engine. It also does not release carbon monoxide like a gas engine, making it slightly safer. Diesels also have more torque, which makes them slightly stronger than comparable gas engines.

The downside to owning a diesel engine is that it is heavy. Typically, only large boats over 10 metres in length use a diesel engine. Smaller boat owners choose the less powerful gas engine because it weighs less, and therefore does not slow them down.

Motor Size

Both outboard and inboard motors come in different sizes. Keep in mind that size here refers to the strength of the engine measured in horsepower, not its physical size. A 4-stroke motor might be larger and heavier than a 2-stroke engine, but the 2-stroke engine produces greater horsepower and torque.

Boat owners should always buy a motor that uses the most horsepower their boat can handle. Installing a small engine on the back of a large boat only serves to make the engine work twice as hard, causing the boat to move twice as slow. Using a low powered engine also affects the boat's handling, making it difficult to navigate through choppy waters.

Motor Power

There are three main types of fuel drives found on boat engines: carbureted, electronic fuel injection (EIF), and direct fuel injection (DIF). Each fuel drive is differs in how it delivers fuel and affects the motor.


Fuel Economy


Comparative Price





Electronic Fuel Injected




Diesel Fuel Injected




A basic understanding of these three systems helps buyers select which one they want for their motor. Without the proper research, a potential customer is putting themselves in a compromising situation.


Carbureted motors are the oldest type, and they are the culprits behind the notorious low-fuel economy of 2-stroke engines. A carbureted engine uses the completely mechanical process of controlling air flow and fuel by a carburetor that sits on top of the engine. These are usually the most affordable models, and buyers who only need a backup engine, or a main engine for their small boat, cannot go wrong with the price.

Electronic Fuel Injection

Electronic fuel injection (EFI) uses electronic controls, air induction, and a fuel delivery system to power the motor. These engines are complicated and complex, which results in them being more expensive than carbureted motors. An electronic fuel pump maintains pressure on the fuel delivery system, which is regulated by electronic controls. The control system measures how much air and fuel need to be injected into the motor at once. These models are more fuel efficient than carbureted engines and are good for powering medium sized boats.

Direct Fuel Injection

Direct fuel injected motors do away with the extra parts of an electronic fuel injected motor. They directly shoot the fuel into the engine's cylinders. Most models come with high quality fuel pumps and powerful fuel injectors, and this is reflected in the overall price. The engine itself automatically adjusts to different temperatures and most models come with a sealed fuel system. This is the most fuel efficient system and well worth the high cost for hard-working boats that need the extra boost.

Buying Boat Motors on eBay

Now that you understand the different types of boat motors, you should look at buying your own. eBay is a great place to start simply because the selection of boat engines is unmatched. You can find the top name brands from all around the world, and even get a great deal on a used or restored motor.

The easiest way to gauge what engines are available is to type 'boat motors' into the search box. This provides a full list of all current motors for sale. At this point, you can start narrowing down your search based on the type of motor you want. For example, search for 'outboard boat motor' brings up results for outboard motors only. Looking for '2-stroke outboard motor' causes the search engine to only display results for this specific type.

Another option is to search for used motors, as this often saves you plenty of money in the final sale. Type 'used boat motor' into the search engine to pull up all relevant results. Make sure the listing is for a working motor, not a used engine that is being sold for parts.


Besides the boat itself, the engine is the biggest boating accessory purchase for owners. Deciding on the right motor is not a process that should be taken lightly, as buying the wrong type could lead to disaster at sea. Before customers start browsing through eBay looking for motors, they need to understand a few key concepts. Motors come in four main types. The 2-stroke and 4-stroke engines are both outboard motors that are mounted on the stern on the boat.

The 2-stroke and the 4-stroke engines are ideal for smaller vessels that require a limited amount of power. Larger boats need the additional horsepower and torque of internal gas, or a diesel engine that allows them to plough through the sea. The size of the motor should be within the upper capabilities of the vessel; otherwise too much strain is placed on the engine. Once all of this is figured out, customers can start evaluating the different power options that include: carburetion, electronic fuel injection, and direct fuel injection.

Have something to share? Create your own guide... Write a guide
Explore more guides