CXO300 the revolutionary diesel outboard for power, economy and durability.

Let’s just say that the CXO300 engine produced by the English company COX Powertrain founded in 2007, by the motor racing engineer David Cox, is a revolutionary outboard motor and already before being marketed, it was awarded the prize by the ADI (Industrial Design Association) ) among the best design products for the year 2018.

It is fully fueled by diesel and has enormous maximum torque even at low speeds with very low fuel consumption.

It is the world’s first diesel outboard capable of delivering 300 horsepower to the propeller shaft at around 4,000 rpm.

In addition, the engine has low vibration, exceptional acceleration for gliding with reduced times and super smooth performance, with limited operating noise, but weighing more than that of a petrol equivalent.

The CXO300 is a diesel outboard engine designed immediately for marine use from scratch. Cox’s team of engineers, led by Stephen Moore in collaboration with the famous British engineering specialist Harry Ricardo, who practically worked with everyone from McLaren Cars to Bugatti, spent over a decade developing and perfect the engine. With months of final tests both in the water and in the laboratory before production, which began in the fall of this year 2019 and will also be the highest power density outboard ever created for a maritime application.

Made with a brand new 60-degree aluminum-alloy head block to save space, it is a 4.4-liter four-stroke V8, the most interesting thing is that this engine develops a maximum torque of 479 foot pounds (ft. Ibs ) corresponding to 649.437 Newtons per meter (Nm) already between 1,300 and 3,000 rpm and the manufacturer Cox claims that it is almost twice the torsion power of its 300 hp petrol rivals.

It is powered by a common rail high-pressure fuel injection system with two turbochargers that make the engine develop an impressive 300 bhp at the propeller with the crankshaft peaks at 338 bhp, truly exceptional performance.

Among the main features is its ordinary maintenance, in fact the CXO300 has been designed for maintenance plans spaced between them, with all the oil changes and replacement of the possible filters, which can reach up to 1,000 and 1,200 hours so initially this is the autonomy time with the engine in the water, thus reducing the need to pull the engine out of the water every 100 hours, as is usually the case with the current petrol outboards. In addition, a post-sales assistance service is available that allows the cancellation of the boat stop in the event of a fault, thanks to the ability to immediately offer a spare engine through a worldwide assistance network supported by 35 marine diesel specialists.

The savings for estimated maintenance costs are around $ 195,000 thanks to fuel savings, lower maintenance requirements and a life expectancy three times longer. This is because the block has been mounted vertically so that the energy is delivered directly along a steel shaft to a universal joint that brings energy to the propeller shaft. The gearbox was over-constructed to cope with the torque and increase its durability. Consequently, it is claimed that it has a life expectancy up to three times higher than a petrol engine and is at least 25% more efficient in terms of fuel consumption.

Despite the great effort to contain the weight and the dimensions, the CXO 300 is not only the most powerful outboard diesel engine in production but also the heaviest in the class of power of belonging due to the engine block that must necessarily be built more consistent to support the high compression ratio characteristic of the diesel engine is why the CXO300 weighs about 375 kg, more than 100 kg more than the average of equal petrol powers such as Verado 300R Mercury.

The cost of the CXO300 is around $ 54,000, including about 20,000 dollars more than a petrol outboard of equal power, so we find ourselves in front of an outboard that is heavier and initially more expensive but also more efficient and should last longer  compared to a petrol outboard. These are the factors that most attracted attention among end users and operators in the sector.

However, Cox is hopeful that over the life of the engine, savings from fuel and maintenance requirements will offset the initial cost.

The steering and throttle controls are all provided by Sestar Solutions, including the ability to mount a joystick control for dual engine applications.

The engine is contained in a sturdy and lightweight carbon fiber grille available in white or black with a modern clean fresh design created specifically by industry specialists to house all the elements that make up the CXO300.


The final image of the engine was advertised prior to this year’s production launch. Among other things, an engine born after a development program that lasted 10 years certainly could not overlook the aesthetics of its external casing that looks stylistically beautiful with its elegant air intakes.

In this regard, Cox Powertrain’s director of global sales, Joel Reid released the following statement:

“Although exceptional performance, fuel efficiency and cost-of-ownership savings are undoubtedly the main features of the CXO300, we believe it is important that its bonnet should not only be the strongest, strongest and lightest possible, but it should also look fantastic. Current trends see a more creative style for high-end outboards like the CXO300 and many customers want engines that are as beautiful as their boat. That’s why, in addition to our standard black and white options, custom colors and stylish wraps will be available in the future “.

  The first deliveries are expected by the end of the year 2019 and since the Company decided to accept bookings since November 2018, there have been numerous orders. When the production line is fully operational, two shifts a day are planned to meet this enormous demand. Cox has invested as many as 6.7 million pounds in the creation of its new production facilities that include an integrated MES (Manufacturing Execution System) system that will ensure the highest standards.

Cox Powertrain’s director of operations, Jerry Attridge, said: “This is a very exciting time for everyone at Cox Powertrain. Not only is the CXO300 a superb and innovative product, but we are also creating a complex, high-precision manufacturing facility that uses cutting-edge technology to offer what can be described as a revolutionary product in the marine outboard market. Fortunately, we have created a fantastic team of people that I’m sure will provide a transformative product. “

  The first series of tests of validation of the outboard in the sea was done on a 9-meter RIB supplied to the American Navy which equipped with two engines CXO300 reached a cruising speed of 43 knots at 3,600 rpm, the Naval testers Sea Systems Command (NAVSEA) expressed great enthusiasm for their performance.

  In this regard, Joel Reid commented:

“This first round of the field validation program went very well and exceeded all expectations. NAVSEA testers seemed impressed by the fluidity of the engines and the absence of noise and smoke, which are historically associated with diesel engines. We are pleased that the two CXO300s have exceeded the target to reach a cruising speed of 43 knots “.

  As initially reported the CXO300 won the ADI award, the award is a recognition for the best design products of the 2018 edition, with an official ceremony held during the last Genoa Boat Show in collaboration with Ucina Confindustria Nautica , the jury he considered it the only engine worthy of this award, for its technical and aesthetic characteristics, as well as for the sustainability criteria with which it was designed. In addition, the English company Cox Powertrain was announced as the winner of the Marine Power and Propulsion category at this year’s Seawork International Innovation Award 2019 also for its revolutionary CXO300 engine because the judges appreciated the originality of the creation where the Cox designers have chosen complete innovation in all aspects without starting from the modification of pre-existing elements.

Main technical features

Engine designation: CXO300

Crankshaft power: 338 hp (252 kW)

Propeller shaft power: 300 hp (224 kW)

Engine propulsion speed: 3700 – 4000 rpm

Number of cylinders: 8

Compression ratio: 16

Weight: 375 kg.

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