What is an outboard engine?
An outboard engine is a propulsion system that can be used for powering a number of boats, including sail boats. It is the most common method of powering small vessels and can provide a number of advantages over other alternatives. The system is affixed to the outside of a boat, as opposed to an inboard motor, which is normally much more permanent. The advantage of an outboard motor is that it can easily be detached when not in use. This saves a lot of space on small boats and is one of the reasons they are perfect candidates for use on small sailboats.
An outboard engine offers a self-contained solution to the propulsion of small aircraft. Before the outboard engine, sailboats would have to rely on manpower alone to sail the seven seas. The invention of outboard motors in the early 20th century has been described as providing boats with the same freedom that the gasoline engine gave to cars!
The first outboard engines worked on electric power and these are thought to have been designed around 1870, by a French Engineer named Gustav Trouve. The much more commonly used type of outboard engine, that are still used today, powered by gasoline came about some years later and were patented by Ole Evinrude in 1928, with substantial improvements made by Carl and Oscar Hult from Sweden.
How does it work?
The same basic principles of a car engine are applied for use in the outboard engine. A gasoline engine will produce power and energy to turn the wheels by burning gasoline with oxygen in metal cylinders, which drives pistons. The pistons are attached to a crankshaft, which in turn are attached to the wheels, providing power.
The process in outboard motors is very similar, the cylinders, of which there will be much less of in an outboard motor, which will be attached to a spinning propeller, as opposed to the wheels. The spinning propeller provides the propulsion to drive the boat through the water.
The diagram above shows a very simplified version of an outboard engine/motor and how it works. IT can be seen that at the position labelled 1, a mixture of fuel and oxygen is ignited, similar to in a car engine and the energy output from this causes horizontal motion of the piston with the cylinder at position 2. The cylinder, moving backwards and forwards is connected to the crankshaft at position 3 in such a way that horizontal motion equals rotational motion. This is then translated to the propeller, making it spin and providing the propulsion to drive the boat through the water.
The benefits of an outboard engine are that they take up no storage within the actual boat. An in-board engine will normally be built into the actual boat and this means that the space taken up is permanently lost as they can’t be easily removed. An outboard engine takes up less space for two reasons. Firstly, the engine over hangs the edge of the boat and therefore no internal space is taken up. Secondly, the engine can also be removed so any obstructions it may cause or any small space it could have taken up on the boat can be removed when the boat is stationary.
The engines also offer great usability and are very easy to fit and operate onto a new boat. On top of this, the controls to guide the boat are intuitive and simple. The only downside of an outboard engine is of course the amount of power supplied means that not all boats can be powered in this fashion and the engine is only suitable for smaller vessels.
Larger boats will need a much larger engine in order to provide the required propulsive force to drive them through the water and this is where larger, built in engines are used. However, for convenience and storage, the outboard engine really is the one to go for, if you have a small enough boat to be powered. In fact, the single most important deciding factor between choosing an outboard engine or an inboard engine is the boat on which it is to be fitted.
From a maintenance point of view, both inboard and outboard engines are relatively easy to repair and there is also no discernible difference in the fuel consumption. However, the boat on which the engine is to be fitted or is already fitted will have been designed with a specific engine type in mind. This means, that a boat that has been designed for an inboard motor may not have the right left of stability for use with an outboard motor. For the opposite, a boat designed for an outboard motor will not have the necessary foundations and structure in place to support an in board motor. However, it is much easier to use an outboard motor on a boat which originally had an inboard motor than it is for an inboard motor to replace a boat designed for an out board.
Picking an outboard engine can be extremely hard with the huge range of different options that currently exist, which may or may not be suitable for your boat. Traditionally, the choice for an outboard engine would be between either a two stroke system or a four stroke system.
2-Stroke Vs. 4-Stroke
The two stroke system was much more lightweight and offered a very simple method of providing power and are normally less expensive and make the boat more agile and in quite a few cases, faster! The two stroke engine is a lot more affordable for those starting out and should something go wrong, they are normally easier to repair than a four stroke engine.
The four stroke engine will provide a smoother ride for the passengers and are generally much more fuel efficient. As a result, the four stroke engine is much more reliable and much less noisy, however they are much larger, much heavier and more sophisticated, which mean the price is inevitably higher as well. The fuel economy can be anywhere from a 10% increase on some two strokes all the way up to a 75% increase on other two stroke engines, which can save a lot of money for a boat owner if they making a lot of trips.
Engines of the future
In the modern era that looks to tackle climate change however, there is a new type of engine on the block. Similar to the way cars are going, outboard engines are too making the switch to much more environmentally friendly power sources, such as electricity. With specialist companies such as Torqeedo specialising, these could be the thing of the future. These can make the maintenance costs of a boat substantially lower and these engines are becoming more and more common and a real option for all boat enthusiasts. Currently, electrically powered outboards are mainly used on some very small craft or as a secondary means of propulsion on some larger crafts.
Other lower emission options include a Propane engine, which was first produced in 2012, a relatively new development with much lower maintenance than traditional engines, as being much more green, these engines can provide power up to 5 hp and so are currently only suited to smaller boats.
Making a Decision
When choosing an engine, this is the first decision that should be made and this will, or should be mainly based on the type of boat that you own, in terms of the size and the planned usage for the boat. The range of power is also huge in terms of what an outboard engine can provide is also huge. A four stroke engine will look to provide horsepower all the way down from 2 horse power and all the way up to around 350 hp. Larger outboard engines are also available, with V6 and V8 engines that could be used on boats over 11m long, delivering over 500 hp!
Sailboats with Outboard Motors
In general, boats which have outboard engines are much smaller than those which have inboard engines. It is generally thought that boats up to around 27 feet can be powered by outboards and this is generally preferable for these smaller vessels, for the reasons and benefits that have been aforementioned in this article. If a boat is above 27 feet, then it will generally be powered by a much larger in-built in board system for more fuel efficient journeys, providing the boat with more propulsion.
There are a few examples of large sailboats that can be found with outboard motors and in general, these will be equipped with more than one motor for power and reliability.
This is an example of a typical boat size and type that can and is powered by an outboard engine. This boat delivers 600 Horsepower in total by having two Verado 300 hp outboard engines. These engines are four stroke engines and they are supercharged. The fuel used on these engines is Gasoline. This boat is just short of 10m in length and this makes it on the larger size of sailboats that are powered by outboard engines. The boat is worth around £30,000 in today’s market. Besides boat trader we’ve seen it listed on auction sites like ebay.
The Oceanmaster 605 Sport, made from a fibreglass material is another example of a sailboat powered by outboards. This slightly smaller boat weighs around 800 Kg and is fitted with a Mercury four stroke engine, which delivers around 115 Horsepower.
This timeless boat is a little older than the two described above. This boat is powered by gasoline, much like the other two and is 20 feet in length. These boats were produced in the 1970s and are still being used today, fitted with a 4-stroke Honda 15hp outboard engine, that is easy to operate, this spacious boat is a good example of a sailboat fitted with an outboard engine.
This boat is more luxurious and comfortable than the other boats that have been described in this article and perhaps more up market. This boat can reach a cruise speed of up to 20 Knots and is powered by a single outboard engine. The outboard engine used is a Yamaha F115 BETL with electric start. It is quoted with good fuel consumption of around 4.5 gallons per hour and delivers up to 115hp. The boat is nearly 19 feet in length.
The Top 5 Outboard Motors For Your Boat
It has already been stated that the right outboard motor that is to be chosen should be one that is fit for purpose. It is the purpose of this review section to try and cover a whole range of out board motors in terms of their power and their application.
Starting with one of the best selling, most prolific and high performance outboards out there, the Yamaha F300 engine really is top of the range in our opinion.
This engine boasts one of the most sophisticated systems that an outboard engine can have on the market today and at $22-25k it is definitely a premium engine. The 4-stroke V6 engine provides a smooth ride for any application and delivers 300 Horsepower, for both performance and comfort. The fuel consumption on this engine will vary on speed and of course the boat it is powering but can get as much as 2.4 litres per hour. We are fortunate enough to have one on the back of our Fisher 605 and we absolutely find it irreplaceable.
It wouldn’t be in keeping with the modern climate and current sign of the times if an electric outboard engine wasn’t included in this list. Having said that, the Torqeedo Travel 1003 C isn’t just in here as a novelty prize, it earns its place as one of the best engines you can buy for small scale applications. By contrast, this engine can be bought for $1500-2500 depending on how new/used.
This engine is ultra easy to both assemble and reassemble and thanks to the latest technologies in Lithium batteries, can run for up to 16 miles at low throttle after one charge. This new and clean way of powering boats will help keep maintenance costs down and offers unrivalled flexibility, convenience and space saving, capable of powering boats up to 1.5 tonnes, delivering 3hp.
Available for $1200-$1700, the Honda BF6, which has made huge leaps forward from its predecessor, the Honda BF5 is an affordable engine, which is available as a 4, 5, or 6hp engine. This engine really is fantastic value, with a low weight of only 27 kg, it is portable and it really offers the full package in terms of smoothness and fuel efficiency.
Another high performance engine, which is a major rival to the previously mentioned Yamaha F300, the DF350A delivers 350 Horsepower, with it’s 4.4 litre V6 construction, boasting the latest innovative technology that is packed into the top of the range outboards, capable of delivering a huge range of different boats.
The technology on this boat has been praised for providing the user with much improved directional stability, as well as an improved ability to make manoeuvres when at low speeds. At $28,000 it is expensive, however this is reflective of the true quality and innovation that has gone into the design and production.
The Mercury Mariner F60 shows a different type of engines to the rest, as middle of the range, delivering 60hp and on the market for $6k. This four cylinder, four stroke engine provides the option of powering medium sized vessels and the Mercury brand has long since been associated with reliability, as well as performance. They have a full range of engines right form the small sizes, all the way up to the largest sizes, which rival that of the Yamaha and the Suzuki engines seen in this section.
In the following article, a comprehensive review of the outboard engine for boats has been completed. The outboard engine can generally power boats up to around 27 feet in length, at which point an inboard engine is normally preferred. The article has covered the basic operation and how these engines work, the disadvantages when compared to other types of engines and has also tried to capture the vast range of engine sizes and types that are available. Some examples of boats that are powered by outboard engines have been provided and finally, a review of the top 5 outboard engines for sailboats has been carried out.
In summary, the selection process for choosing an engine for a given boat is complex and many factors should be considered. The main factor is of course the type of boat and what engine types it can support, followed by the size of the boat and the amount of power that is needed. Outboard engines provide a great source of power for a large range of boats and recent developments have seen impressive leaps forward in performance and efficiency, which will continue in the future with the development of the next generation of outboard motors.