Superyacht News Magazine 

By Megan Hickling
19 Jul 2024

A cleaner marine engine
Barry McCooey of M&H Engines explains how its Stage-V marine engines provide significant emissions reductions despite being a typical diesel engine…
M&H Engines’ latest range of diesel engines may be a typical internal combustion engine (ICE), but it is an interesting example of improving something that traditionally has high emissions and developing that technology into a reduced-impact-emissions option. Barry McCooey, Managing Director of M&H Engines, explains: “We started out in 2017 to build the world’s cleanest marine engine”, which is what they have managed to achieve with the development of their M&H Stage-V marine engines.

As shown in the graph below, the M&H engine is well below the emission limits as set out by non-road, mobile machinery (NRMM) regulations by the EU. NRMM Stage V, effective since 2021 and applicable to land-based non-road purposes rather than maritime engines, has much more restrictive emissions limits than IMO Tier III, for example NOx, which is 7.7g/kWh, while NRMM ranges from 0.4 g/kWh for engines rated between 130 and 560kW and 3.5 g/kWh for engines rated over 560kW.

Emissions reduction

To achieve this significant reduction, M&H went into development with the attitude of “let’s look at all the best technology available in all the industries and find the best products and best solutions for us”, says McCooey.

There are a few different aspects of the design of these engines that allow for decreased engine emissions.

One of these is the ability to keep the exhaust gas temperatures high while maintaining a surface temperature of under 220 degrees Celsius, compliant with the IMO SOLAS requirement. This higher temperature enables more efficient post-combustion treatment to reduce the harmful elements in the exhaust. This has been achieved through heat shielding and other patented design aspects.

A bigger difference from other typical ICE diesel engines is the power and torque characteristics of the engine. McCooey explains that this facilitates choosing the right engine for the job, providing engine optimisation through correct engine operation, leading to better fuel consumption and reduced emissions.

This different power curve is best demonstrated by comparing a M&H 317kW (425hp) engine to a John Deere Tier III 410kW (550hp) marine engine, which shows a few advantages. While having 125hp less rated power, the M&H engine provides more power up to 2,200rpm and more torque up to 1,700rpm. After these points, the Tier III engine matches the power, and can provide more torque. However, this is at the cost of burning more fuel to achieve this – 7 l/h more at 1,700rpm and 28.8 l/h more at 2,200rpm – making the M&H engine preferable at medium and lower speeds. This will require a shift in thinking away from aiming for top speeds that will rarely be used.

Alongside the fuel efficiency this characteristic can provide, it also means the potential for a smaller, less heavy engine on board, which can offer more design freedom.

Alongside these fundamental differences in the engine which improve its output, leading to the significant reductions seen in the graph, there are additional actions that could be implemented on other ICEs. A typical addition is that of AdBlue or urea to reduce the NOx emissions from the engine even further. While urea has environmental issues, such as being associated with its production and its potential to contaminate the environment, the M&H engine has one of the lowest AdBlue consumptions on the market.

A further addition recommended for use by McCooey is Super Lubrication Ltd Mechanical Treatment System (MTS). Rather than a chemical reaction, this treatment reduces the friction within the engine, gearbox and other mechanical elements. This reduced friction has multiple benefits. Primarily, it will improve the engine efficiency as less fuel is needed to overcome the friction to achieve the same results.

“We future-proof our customers for the next two or three emissions regulations.”

In a test on a Princess S72 yacht with twin V12 MAN diesel engines, the savings proved to be around 10 per cent. Reduced wear also means increasing the service life of the engine and reducing the need for engine maintenance. There will also be noise reduction from the smoother operation.

The final product recommended by M&H to be able to achieve the maximum impact reduction is the use of the synthetic, carbon-neutral diesel fuel C14-16, which is produced using captured carbon, but has the same density and performance as typical diesel and contains no sulphur or bulking agents.

While this doesn’t change the direct emissions associated with the vessel, the carbon used in its production should equate to the amount being captured for its production, hence being net zero, as well as ideally being produced using renewable energy, thus reducing its associated emissions compared to typical diesel. This synthetic diesel can entirely replace or be blended with regular diesel or other diesels such as biodiesel.

While biofuel is still more environmentally friendly and more circular, its lower potency can mean larger fuel tanks/more refuelling. The other environmental advantage, McCooey explains, is that C16 will entirely break down non-toxically in seawater. He also stated how this fuel can be produced in a scalable and local manner as it doesn’t require large amounts of space for the processes, and the main demands are suitable electrical power, water (to be split into hydrogen and oxygen) and captured carbon.

McCooey hopes to develop a consortium to produce this fuel in bulk, as it is capable of providing both carbon capture and fuel to areas and corporations who build these production facilities, potentially relieving marinas from reliance on the national grid.

This fuel treatment echoes the M&H engine in terms of it being an alternative solution that isn’t so different compared to the typical less sustainable version but still provides significant environmental impact reductions. Other more recognised and familiar environmentally friendly propulsion options receive more attention, focus and development as people look to gain their environmental savings. While this is an appropriate development for many, in some cases, it isn’t suitable to the vessel or location of operation, or in other situations where there could be increased negative impact due to the associated emissions in the production and transport of the fuels and supporting infrastructure.

These extremely low-impact diesel engines are a great middle ground which can provide environmental savings. However, this will be reliant on people understanding that while it is a diesel engine, that doesn’t automatically rule it out as a solution for reduced emissions. This is where McCooey feels that the key to adoption is “education, education, education”, as he says that M&H have presented this engine range to the market for three years and it’s only this year that it’s gained traction and is going somewhere, as people finally understand and see the benefits to be gained.

McCooey says the maritime industry is “30 plus years behind on-road and off-road technology”, but still foresees that, eventually, other engine manufacturers will catch up with this type of technology. MCooey theorises it has taken this long due to the attitude within the maritime industry of, as he summarises it, “We’ve always done it that way”, leading to a lack of change and development. However, from experience, he says superyachts have been more willing to change, but only once understood the savings to be made have been understood.

The benefits could incentivise many to install these low-emission engines and develop similar models. In their mission to achieve the cleanest engine in the world, these engines have not only met but significantly exceeded multiple emissions regulations, such as IMO Tier III, NRMM and California Air Resources Board’s Tier IV emissions limits. As McCooey says, “We future-proof our customers for the next two or three emissions regulations”, meaning that those adopting low-emissions solutions such as these will avoid more changes in order to be compliant with future regulations or the penalties that could apply from non-compliance.

The drop-in-ability of the M&H engine – and the need to meet future emissions limits – means that it could well be a more favourable method for reducing emissions. If it was adopted during superyacht refits, the cumulative impact reduction potential would lead to a significant amount of emissions reductions during subsequent operations.

As all sustainability options, these engines won’t be the perfect solution and, in some cases, the other more environmentally friendly options will still be preferable, but the opportunity to implement them on those less willing to change design while still achieving reductions seems one worth taking for many.

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A cleaner marine engine
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