What Is An Outboard Motor

Whether you’re new to boating, or a seasoned professional who’s considering the purchase of an outboard engine, you’ve come to the right place. In this article, we will discuss the basics of the outboard motor, the main types of outboard motors in production, the pros and cons of fuel-powered vs electricity-powered, the components of the outboard motor, and how the outboard motor actually works. 

Outboard Motor Basics 

There are several types of marine propulsion systems available. These include inboard, outboard, and sterndrive motors. While all three have a selection of similarities and differences, one obvious distinction is where they are placed on a boat. 

Differing from an inboard engine, which is usually hidden inside the boat, an outboard motor is a propulsion system that is installed fully on the outside of the hull. It can usually be found fixed to the exterior of the transom, powering the boat. A sterndrive on the other hand is a combination of inboard and outboard features.

In addition to propulsion, an outboard engine also offers steering control as it’s built to adjust the thrust’s direction by pivoting over its mountings. The outboard motor is often the top choice for fishing, light commercial inshore boats and recreation as the engines are easy to use and reliable.

Types Of Outboard Motors 

The outboard motor engine can be divided into two categories, the fuel outboard motor and the electric outboard motor, each powered by a different energy source. 

A Petrol Outboard Motor 

Petrol outboard engines are typically seen on large boats in the marine industry. If the continued cost of fuel isn’t a concern, and you can work with the noise the motor emits, then a petrol outboard is ideal for providing both power and speed. 

That being said, electric propulsion in boating has become more widespread and is constantly improving. Due to ongoing innovations, the market now has a variety of long-range, high quality and large-horsepower electric motors.

An Electric Outboard Motor 

Unlike its counterpart, the electric outboard motor provides a clean, quiet and innate solution, along with lower maintenance making your boating experience nice and satisfactory. 

Note: people often mistake the electric outboard for a trolling motor when referring to small outboards. Unlike a trolling motor, which works as an auxiliary power at slower speeds, the electric outboard motor can be used on larger vessels and sailboats in addition to small boats.

Lithium batteries have made today’s electric outboard engines not just equivalent to fuel engines, but better than them, for most users.

In the world of recreational boating, the electric outboard motor is gradually becoming the preferred choice when compared to traditional petrol outboards, particularly among small and medium-sized boat owners.

Components Of An Outboard Motor 

The outboard motor is a common choice on boats. Being aware of its different components is critical to better operating the watercraft and being able to carry out maintenance and repairs. 

The Petrol Outboard Motor 

A petrol outboard motor is primarily made of five components: the engine, clamp bracket, gearbox, body components and propeller. 

  • Engine comprises two major mechanisms and five systems-
  • Two Major Mechanisms: the valve mechanism (camshaft, ejector rod, valve, etc.) and the crank connecting rod mechanism.
  •  Five Systems: namely the fuel supply system, ignition system, starting system, cooling system and lubricating system. It includes a crankshaft, piston, connecting rod, cylinder liner, cylinder block, cylinder head, cooling system, fuel system, intake system, lubrication system, and accessories, etc. 
  • Clamp brackets are a set of structural parts that fix the outboard motor to the stern plate of the boat and also provide a complete set of structural parts for lift and angle adjustment of the outboard motor.
  • Body Parts are structural parts that fix the engine and gearbox and have the function of silencing the engine exhaust;
  • Gearbox is a set of shafting structures that transform vertical rotation into the horizontal rotation of the propeller and provide a reduction ratio. It also includes the shifting mechanism and the gearbox housing. The internal combustion engine of the fuel motor has poor torque and excessive speed, making it unsuitable for boat propulsion. Hence the gearbox is required to boost torque while lowering speed.
  • Propeller is a device that converts the rotational power of an engine into propulsion. For a heavy loaded boat, we usually prefer an outboard motor that can provide a large torque, large propellor pitch and high propulsion efficiency. For lighter boats, the torque requirement is lesser, the speed is higher and the propeller pitch is smaller compared to their heavier counterparts. Smaller boats have higher fuel economy due to higher propulsion efficiency.

Irrespective of the horsepower, all petrol outboards have a top-mounted structure. This means that the engine is mounted on the upper section of the outboard, along with the shifting mechanism and transmission.

The Electric Outboard Motor 

Compared to the complicated structures of the petrol-powered outboard engine, an electric outboard has a much simpler structure. Electric outboards have fewer parts, are safer and easier to store, don’t leak or smell of petrol, and can be stored mindlessly (so you can stow it away in a cabin for security). 

The core components of an electric outboard are the motor, the battery, and the control circuit that commands the speed of the motor. The motor is used to both power and maneuvers the boat, and so, to steer you need to move the entire engine. Unlike larger outboards, which have a steering wheel, smaller boats often use a tiller steer to change direction. 

Depending on the position, the electric outboard motor can be divided into 

  • the under-mounted type motor (suitable for electric outboards with smaller horsepower) and, 
  • the upper-mounted type motor (suitable for electric outboards with larger horsepower).

Difference Between An Electric Outboard And A Petrol Outboard Motor

You may be wondering why both motors work so disparately. Let’s take a look at their work principles and find the differences between a petrol outboard motor and an electric outboard motor.

The Petrol Outboard Motor 

In a petrol outboard motor, the petrol and air are mixed by a piston-type internal combustion engine and burned in a cylinder. The heat released can generate high-temperature and high-pressure gas in the cylinder. The gas expansion pushes the piston to do work, and the mechanical work is output through the crank connecting rod mechanism. This is then converted into the kinetic energy of the boat through the mechanical transmission and the propeller, pushing the boat forward. If you’re on the lookout for a boat with a large engine for gliding, then you would be right to consider a classic combustion engine. 

The Electric Outboard Motor 

More electric outboard motors are now being imbued with the ability to use their batteries as an energy source. This works by converting electric energy into kinetic energy, through the electric motor. 

Range anxiety is a common topic when it comes to electric-powered boats. ePropulsion pioneered the use of hydrogeneration to overcome and release this concern in electric outboard engines. Hydrogenators can empower sailors, allowing them to collect electricity from wind and water, with a hydrogeneration function.

It is suitable for both saltwater and freshwater and can provide propulsion for dinghies, cruising sailboats, daysailers and aluminium fishing boats.

Based on its components and work principles, we can easily see that a boat equipped with an electric outboard motor is emission-free, releases no unpleasant smells, is mostly maintenance-free and amazingly silent. They also remove the fear of petrol driving bans on the water, while not scaring off wildlife.

When you’re on the lookout for a boat to enjoy nature and relax in, an electric outboard motor is just the thing for you! Besides, it has an economic advantage for frequent drivers due to its significantly lower operating costs.

Electric outboard motors are an appealing alternative to petrol motors, especially for small engines. 

Advantages Of The Outboard Motor

Of all motors on offer, especially those used for small and medium-sized boats, the most frequently used method for motorising and operating a boat is an outboard motor. It’s an effective means of cruising in the water due to its propulsion system. 

Unlike the sterndrive (also known as the inboard/outboard motor) or the inboard motor, the outboard motor can be fully detached for repair or storage purposes. This is a great feature if you need to retrieve the engine from water to reduce erosion or need to avoid obstacles in shallow waters. It can also help when winterising a boat. 

Between the electric and fuel engine, the electric outboard offers greater benefits than the fuel. Primarily, an electric outboard motor has a lesser number of parts. In particular, it doesn’t contain a carburettor to ‘stuff up’ (the most common cause of petrol motor issues as petrol contains Ethanol). 

Secondly, although electric outboards are undeniably more costly than petrol-powered ones, mostly because lithium batteries are expensive, an electric outboard offers lower running costs over its lifetime, in part due to it needing little to no servicing. 

Thirdly, if you’re after efficiency, outboards are superior due to their power-to-weight ratio. Outboards weigh less than inboard engines, improving gasoline efficiency and performance.

Disadvantages Of The Outboard Motor 

In the past, a common complaint about the outboard engine was how noisy it was. However, the outboard also comes in an electric option, offering a much quieter experience. With the introduction of electric-powered motors, the issue of noise emittance by both 

inboard and outboard motors is being progressively addressed. If you cruise in an electric outboard motor-powered boat you’ll enjoy the sounds of nature rather than the roar of an engine. Therefore, for small boats, or maneuvering when fishing, an electric outboard is an ideal option. 

The other disadvantage is that an outboard engine creates larger wakes than its counterparts. 

If you prefer a perfect swimming platform or you enjoy skiing and other watersports, the inboard engine is more suitable as it has major towing power, better wake control and an unobstructed transom for tow ropes.

To Wrap It Up 

As opposed to an inboard engine that is usually hidden inside the boat, or a sterndrive which is a combination of inboard and outboard features, an outboard motor is fully installed on the outside of the hull. It can be found mounted to the exterior of the transom and comes in a petrol-powered form or an electric one. 

As with anything, an outboard motor comes with a variety of advantages. For instance, it can be fully removed from a vessel for storage or repair. This is a great feature if you need to avoid obstacles in shallow waters or are looking to slow down erosion. 

Petrol outboard engines, however, come with several disadvantages, one being that they are very noisy. This can create barriers such as scaring wildlife away or just distracting you from the sound of nature. However, modern, electric alternatives not only counteract this hurdle but also provide many more advantages. One such advantage is hydrogenation, a feature pioneered by ePropulsion which allows you to use your battery as an energy source

How Can We Help? 

If you’d like to find out more about hydrogenation, or you’re looking to purchase a boat motor or battery, contact ePropulsion at 1300 590 951, or browse our products here.