Cox’s outboard diesel engine introduced for the Ockelbo B25

In a collaboration with DPower, Ockelbo is outfitting the Ockelbo B25 with Cox’s CXO300 outboard diesel engine. The new engine provides boat owners with a fuel-efficient, clean alternative with great fuel economy and longer service intervals.

Cox Ockelbo

Ockelbo is known for its commitment to crafting top-tier, fully-welded aluminium boats that exemplify both quality and performance. Stepping into uncharted waters, they have now taken a leap towards expanding their engine offer by equipping their renowned aluminium Ockelbo B25 model with an outboard diesel engine. This initiative presents a dependable engine alternative to the market, ensuring an extended operational life and the ability to travel longer distances while consuming less fuel.

“We’re delivering the CXO300 engine from Cox to Ockelbo and are helping out with commissioning and testing the combination. This is the first time we deliver a diesel outboard engine to a Swedish boat manufacturer, and we believe this fills a major gap in the current market,” says Mats Hallberg, Cox representative at DPower.

Excellent performance of a purpose-built marine diesel engine

The CXO300 is a meticulously engineered 300 hp V8 with a 4.4-litre displacement which has been purpose-built for marine applications. Its design and performance are crafted to meet the rigorous demands of marine use, ensuring reliability and optimal functionality.

“In our tests, this setup has performed remarkably well. Loaded with six passengers, it reached over 40 Kn, a speed we can only achieve with two passengers using an equivalent petrol engine,” Michael Waax at Ockelbo says. “This effectively dispels the misunderstanding that diesel is slower than petrol and shows the difference in performance when the boat is heavily loaded.”

The engine is also optimised for long service life and extended service intervals of 250 hours. This can be compared to petrol engines which typically require servicing every 100 hours, have drastically shorter lifespans, and lower secondhand value.

Better fuel economy compared to petrol alternatives

Diesel engines outperform petrol engines at low RPMs due to their higher compression ratio. This greater compression of air and fuel within the cylinders results in increased power output at lower speeds and about 30% better fuel efficiency.

“A better fuel economy is, of course, interesting to a lot of boat owners and businesses. It means a longer range and also alleviates concerns about running out of fuel during extended excursions. This advantage offers a sense of reassurance and convenience, allowing for more uninterrupted and worry-free maritime experiences, especially for those who use their boat a lot,” says Hallberg. “The ability to run the engine at low RPMs also means that the boat offers a quiet and comfortable ride. And in the wintertime, diesel is often more readily available as leisure boating shuts down for the season,” he adds.

Sustainability is a key factor for many boat owners

Beyond lower fuel consumption, there are additional environmental benefits. For example, the CXO300 can be run on HVO or the 100% fossil-free alternative, EcoPar. Emission tests have also shown the engine to be so clean it meets the strictest environmental requirements in Europe.

“The CXO300 has been cleared for use on Lake Bodensee in Germany. That’s typically not possible for engines over 100 hp. It is an exceptionally clean burning engine, and you are now permitted to run twin CXO300 on that very lake. That’s a big deal for a lot of customers in Europe,” says Hallberg.

A wide range of potential buyers

The Ockelbo B25 diesel variant is ideal for both private owners and businesses requiring consistent year-round boat usage. This includes boat taxi operators, medical professionals serving in archipelago environments, and daily commuters.

“We’ve also seen that there’s a great interest among authorities, who usually require a diesel engine. The same is true for boats operating around oil platforms, where you’re not allowed to use petrol engines for safety reasons,” Waax says. “And of course, there’s an interest among companies offering maritime training. Currently, the setup is being thoroughly tested by Anna Sandgren, who is a boat instructor and journalist spending well over 200 hours at sea a year. She is putting the boat through its paces and will be reporting about it in the time to come.”

A collaboration based on dedication to quality

The collaboration between DPower and Ockelbo started in 2023, and the first boats will be delivered in the first quarter of 2024.

“The Ockelbo B25 is an exceptional, handcrafted boat made in our factory in Riga. People are often surprised to learn that it takes 900 hours to make it and that it is welded together by hand by the most highly skilled welders available. Everything is handmade. This is a premium vessel, and we make no compromises with any detail, and that means that all suppliers must live up to the same level of quality as our welding work,” says Waax.

Facts about the engine:


  • 300 hp
  • 4.4-litre outboard diesel
  • 503 lb.ft torque at 2250-3000 rpm
  • EPA Tier 3, RCD II, IMO II and BSO II

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