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Are Diesel Outboards Catching On?


Are diesel outboard engines catching on?

The British diesel outboard manufacturer Cox Powertrain, working with its German distributor, Diesel Power, and Axopar’s German dealer, Boote Polch, commissioned the installation of twin 300-hp CXO300 diesel outboards on an Axopar 37.

According to Cox, the CXO300 diesel outboard engine offers 25% better fuel efficiency, lower emissions, triple the service life, and higher torque in the lower range than a similarly rated gasoline outboard.

According to Cox, the CXO300 diesel outboards were tested on the Axopar 37 during sea trials in Lymington, England, on a smooth to moderate sea, consuming 37.51 gallons per hour at 4,000 rpm, and reaching a top speed of 41 knots. During trials on the Mosel River in Germany in calm conditions, the Axopar 37 reached top speeds of 46.3 knots at 3,900 rpm.

Peter Nauwerck, Managing Director at Diesel Power AB, said, “the combination of the Axopar 37 and the CXO300 diesel outboard is attractive for many market segments including the boat tender sector, geographical markets with a limited availability of gasoline and also for those looking for a dramatically improved range.”

Diesel outboards also allow for a single fuel and lower volatility. Instead of having to carry diesel for a generator aboard a gas-powered boat or carrying gas for a tender on a diesel-powered boat, only one fuel is required. Diesel is also less volatile than gasoline.

Cox says the CXO300 also has lower emissions, producing 20-35% fewer CO2 emissions than comparable gasoline outboards.

The diesel outboards weigh more than their gasoline cousins and are more expensive by horsepower, but according to Cox, with an expected operating lifetime three times longer than a gasoline engine, over time, the total cost will be lower than a gas outboard.


Axopar is not alone in offering diesel outboards. Compact Mega Yachts (CMY), a Finnish start-up, is building two new cruisers which will be exclusively powered by triple 300-hp diesel outboards from Swedish company OXE. CMY says the boats will have an “adaptable powering” mode, which when operating on one engine will give the cruisers a range of about 3,000 nautical miles.

In the “adaptable power” scenario, a computerized control system determines whether to use one, two or three engines and which ones to run for balance. When an engine is not in use it is automatically lifted out of the water.

The CMY161 at 53 feet LOA, and the CMY173 at 57 feet LOA will essentially be the same, except that the slightly longer CMY173 will have a third cabin.

The OXE outboards are marinized versions of BMW’s 3-liter, six-cylinder car engines and like the Cox outboards promise lower emissions, better fuel economy and higher torque than gasoline engines. CMY says diesel outboards are more efficient than gas outboards on larger yachts. OXE says their 300-hp engines can consume up to 40% less fuel than a gasoline engine.


CMY will put the outboards in a locker on the transom. Maintenance can be performed by lowering the engines to access the front, and the gearbox and props can be serviced from the swim platform when raised.

The first CMY is scheduled to be launched in 2022. 



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