‘Pushing OPEX off a cliff’: the new CXO300 diesel outboard

Definitely a wolf in sheep's clothing: Cox Powertrain's new 300hp diesel outboard has been made to look as conventional as possible. Definitely a wolf in sheep's clothing: Cox Powertrain's new 300hp diesel outboard has been made to look as conventional as possible.
Industry Database

“Sitting between an automotive engine and a big power plant,” is where the CXO300 belongs, said Tim Routsis of Cox Powertrain.  As a result, this very new, turbocharged V8 promises to save heavy users hundreds of thousands in operation costs.

Interest in a diesel, not gasoline, outboard was originally sparked by the UK’s MOD but it wasn’t long before the US Coastguard and a number of other defence organisations sat up and paid attention. However, it has taken six years of hard work “to make it from blank sheet to reality” said Routsis, although he added the journey has been worthwhile “because very clearly, the marine sector has been screaming out for something like this... we could see huge demand and knew users would see the benefits very quickly”.

So, why wrestle a large diesel into an outboard? “There’s the safety factor, people, especially commercial operators, are becoming leery of gasoline in boats,” he said. “Linked to this, gasoline bunkering at any scale is subject to some fairly onerous constraints, so logistically diesel is much better.”

There’s another straightforward argument. “The boat simply goes further per kilo... and actually the C02 footprint drops. That’s the hard truth, burn less hydrocarbon per kilometre and you win on environmental grounds.”.

Centrally, however, is diesel’s durability which is hard to match: “These commercial operators, they treat engines as a cost of doing business and just use them up. In many cases the boat is hammering out to site, then it just sits loitering for hours, before hammering back again. The worst of all worlds for engines.” That alone puts maintenance costs up.

On the other hand outboards do retain certain practical advantages: beyond reclaiming space within the hull, outboard engines can be swapped out if there’s a failure rather than sending the boat off charter.

For those that are wondering exactly how you hang a diesel engine from the back of a boat, Routsis said the sheer mass of the engine has also been addressed: “We’ve got within striking distance of the weight of a gasoline outboard: a 350hp engine is generally around 300kg, we’ve come in at 365kg*, so it’s a little heavier, but not by much, so the transom and overall vessel balance won’t really be affected.”

So, how did Cox get there? He explained: “Every single component has been looked at. For example, normal, heavy-duty diesels have cast iron blocks. There’s no way to accommodate that kind of thing on the transom, so we’ve developed an alloy block, designed from first principles, to get the durability and light weight.”

“We’ve also taken out some of the secondary components: for example, the engine has to be cooled, but so does the Exhaust Gas Recirculation (EGR) system that keeps the emissions to within acceptable limits. So we’ve integrated the EGR coolers into part of the engine block itself: just by doing that you drop a few kilos,” he said, and pointed out “if you add enough of those sorts of efficiencies together, you start getting something very impressive.”

Despite this, there’s little in the exterior design to announce the engine’s sophistication: “There’s been a conscious decision to make this outboard look as conventional, non-threatening and as easy to integrate as possible,” said Routsis.

Finally, the figures look convincing. Total Cost of Ownership (TCO) use cases have been calculated for a period of 6,000 hours, taking into account both the CXO300 overhaul at 3,000 hours and traditional gasoline outboard overhaul at 2,000 hours.

Firstly, the ‘windfarm’ case yields a TCO saving of around £202,000 while the ‘ISO Heavy User’ calculation (based on ISO 8178, E5, commercial profile) yields a TCO saving of around £219,000. However, the really big difference is found in the ‘100% Throttle’ use case, in other words, running at full speed, full time. This yields a TCO saving of around £455,000. Routsis pointed out: “Margins like that get attention.”

Together, these factors “make an utterly compelling argument”, he concluded. “A commercial operator will look at the overall lifetime costs - and this engine pushes total OPEX off a cliff.”

The order book for the CXO300 should being opened at the end of this year for deliveries mid-2019.

*It is important to emphasise that the weight stated is concurrent with the final development phase, which is currently being undertaken. The final weight of the CXO300 is likely to be closer to 350kg.

Visit Cox Powertrain at Seawork International 2018 on stand PY65.

By Stevie Knight

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