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Yamaha unveils hydrogen-powered outboard with prototype fuel system

Yamaha Motor unveiled the world’s first hydrogen-powered outboard for recreational boats along with a prototype fuel system integrated into a vessel that the company plans to further refine for testing later this year. (Earlier post.) The effort is part of Yamaha’s strategy to achieve carbon neutrality by deploying multiple technology solutions.

Yamaha joined forces with Roush to develop the fuel system to power the new outboard and collaborated with long-time boat builder partner Regulator Marine to build a boat suitable for testing the prototype outboard. Together, the companies plan to begin testing the protype for viability on the water in the summer of 2024.


By working with Roush on the fuel system engineering, Yamaha gains the benefit of more than two decades of hydrogen systems integration and research.

When you look at Roush’s history with hydrogen, it ranges from land speed record vehicles to spacecraft. A lot of that knowledge we’ve acquired over the years we are now applying directly to this Yamaha project. We are the fuel systems integrator, responsible for fuel systems designs, all of the specifications development, physical integration, safety system analysis as well as testing and development. Yamaha is trying to determine if hydrogen can successfully be used in this market, and I think we will find out the answer is ‘yes.’

—Matt Van Benschoten, Vice President, Advance Engineering, Roush


Regulator Marine built a hull based on the 26XO and modified it to accommodate the hydrogen tanks necessary to power the new outboard. Together, Yamaha, Regulator and Roush displayed the boat hull, fuel system and outboard to demonstrate how hydrogen could work as a possible fuel source in a marine environment. Also, the effort allows engineers to begin the process of determining marine standards for the use of hydrogen in vessels.

If we don’t look for a new source, we won’t find a new source. Innovation starts by asking questions. It creates a little angst, but at the end of the day good stuff comes out of innovation. In the future, as we design boats, if this proves what we think it will, it could be very possible that we are designing hulls around these hydrogen fuel tanks.

—Joan Maxwell, President, Regulator Marine

Yamaha announced the hydrogen outboard project last December. Further demonstrating the company’s commitment to a multi-technology approach to carbon neutrality, Yamaha recently announced plans to acquire all shares of electric outboard company Torqeedo. (Earlier post.) In addition, Yamaha continues to promote the use of sustainable fuels within internal combustion outboard engines as another alternative.



I like methanol for boating, but it looks like many are keen on hydrogen in spite of the need for substantial tanks.

At any rate, the Italians are building 100 hydrogen refuelling stations at marinas


Meh, I couldn't disclose the manufacturer at the time under embargo, but I turned a Yamaha outboard to run on hydrogen, reported on GCC in 2012, as part of my PhD dissertation.


Hi TDIMeister:

I wonder how close Yamaha are to hitting the targets you outlined:

'A gross indicated thermal efficiency of 45% and engine-out, cycle-weighted indicated specific NOx emissions of 1 g/kWh are targeted.'


You might want to read Dr.Oh’s work to get some insights.
Interesting quote:
“ Using hydrogen in internal combustion engines predates even Diesel (1892), Akroyd-Stuart (1890), Otto (1876) and Beau de Rochas (1862), with the work of Rivaz dating to 1807 [1]. “



Several degrees above my head, I am sure.

A man's got to know his limitations, as someone or the other said.

I can add up reasonably well, and consequently can often, or at least sometimes, spot when stuff is being palmed off with big gaps in what they choose to mention.

But technical evaluation of different combustion regimes etc takes a technical education, which I ain't got.



I'm just that irritating little fella from cost and works whose like have crushed a thousand engineer's dreams! ;-)

Just bright enough to get some sort of handle on what they are up to, certainly not at the level of the engineers doing the heavy lifting.

I love them to death, but they should not be let out of the house unsupervised! :-0


The photo above suggests that the Yamaha engine is a fairly high-power unit, appearing to be based on the company's 5.6L V8 producing 425 HP but significantly detuned for hydrogen operation. When we did our market analysis, we didn't see that hydrogen was a good match for high-power, performance boating applications because of the high storage cost and low energy density of the carried hydrogen. The prototype above apparently carries three Type-II or III tanks (giveaway is the fiberglass windings instead of carbon used in Type-IV) each costing a few thousand USD at OEM volumes, with a likely H2 capacity of about 5 kg @ 350 bar each. Fifteen kg of H2 is the equivalent of about 15 US gallons or 58 L of gasoline, which in the boating world is very little - certainly not enough to take a 200 HP boat out for more than a very short time on a typical marine duty cycle (defined by the ICOMIA).




Sounds a very long way indeed from anything practical, although of course this is just an admittedly early stage prototype.
Perhaps they are counting on CF tanks dropping enough to make them a practical option, amongst other things.

I dunno why the Italians are going ahead with the installation of 100 hydrogen stations for recreational boating, it seems premature at best.

Any ideas about what they are up to?


Hi TDIMeister:
I wonder how close Yamaha are to hitting the targets you outlined:
'A gross indicated thermal efficiency of 45% and engine-out, cycle-weighted indicated specific NOx emissions of 1 g/kWh are targeted.'

@Davemart: This prototype almost certainly uses port injection of hydrogen instead of direct injection - the latter of which would otherwise likely need an onboard compressor. So, I don't expect the thermal efficiency to come close to what we achieved as an attempt to approach the scientific bleeding edge at the time. I would guess closer to the PFI-SI-typical mid-to-high 30s percent at the best point. By the way, the efficiency best point of an ICE doesn't coincide with the propeller law curve of a marine engine anyway...

In subsequent research, I found a way to reduce wall heat transfer losses in H2 ICEs by ~50%. We didn't measure the impact of this reduction on the improvement in fuel efficiency as it wasn't the primary objective, but several references on a wide range of different engines put this between 10-25%.

Full texts to papers available here:



!! 10-25% efficiency increase is one heck of a bump!

I have never heard about the possibility of using argon, so am at sea on every count, from the availability etc of argon to everything else.

Hopefully the likes of Gryf and SCJ who are way better equiped can interact with this, as I have no idea!.



Interesting comment about propellor speeds for boats not being in line with combustion engines.

For leisure craft Candela seems to me to own the best tech, with unbeatable energy efficiency as instead of using most of it to shove water aside they glide above it, on foils, at around the same energy consumption to move at of the order of 20 knots as they use at 4 knots before takeoff.

They use electric engines on pods, I have no idea if electric engine propellor speeds are more compatible with then than the issue you outline for ICE.

There are three big issues, the first being weight, with their largest craft the P12 coming in at 12 meters and 9.5 tons.
No idea how much it can scale.

The second is fuel, as they can only do limited distances due to using batteries,
So for longer distances some version of hydrogen/methanol storage would be needed.

The third is of couse cost! ICE of one sort or another and ploughing though the water rather than gliding over it is not going to go out of fashion anytime soon.

Your comments would of course be valuable, as you know what you are talking about, whereas I have read a couple of articles......


"I have never heard about the possibility of using argon, so am at sea on every count, from the availability etc of argon to everything else."
This is a further, separate development from my doctoral work, but it is a fascinating subject, and there are several universities and startups - including mine - working on it, although I am not publicizing our work beyond what has been put out there, yet... These are not intended for on-road transport, but we are talking about net (brake or electric) efficiencies realistically hitting 65%. Google "argon power cycle" for more info. Toyota has published several papers on this subject, including SAE 2010-01-0581.

"Interesting comment about propellor speeds for boats not being in line with combustion engines."
It sounds counterintuitive, but ICEs get their best efficiencies (lowest brake specific fuel consumption - BSFC ) at high loads and low RPMs. For an automotive gasoline engine, this occurs close to 3/4 throttle at about 2000-2500 RPM. Marine loads follow the propeller law, which increases to the square of RPM on the torque curve or to the cube of RPM on the power curve. At steady state 2000 RPM (i.e., not planing) the outboard is just trundling along and is operating far from the best efficiency point.

"They use electric engines on pods, I have no idea if electric engine propellor speeds are more compatible with then than the issue you outline for ICE."
Electric motors do provide high efficiencies over a wide operating range, usually above 80%, but it's not really comparing the same thing because the electrons feeding the motors had to be generated from somewhere with efficiencies considerably less than 100%, and in some places came from a thermal power plant with less than 40%.

"There are three big issues, the first being weight, with their largest craft the P12 coming in at 12 meters and 9.5 tons."
The weight of the vessel is certainly a factor, since there is a direct relationship between its mass and the power/energy required to move it. There is a lot of talk about the weight of batteries, but although hydrogen is a very light molecule, storing it is anything but light. The current state-of-the-art carbon fiber wound tanks still hold only single-digit percent H2 compared to the weight of the tank. That means that for every kg of H2 carried, the tank weighs 10 kg or more, even in the best case scenario.


TDIMeister said:

' There is a lot of talk about the weight of batteries, but although hydrogen is a very light molecule, storing it is anything but light. '

Yeah, but above a certain vehicle weight etc it still weighs way less than sticking in more batteries, which is why just about every transport company with the exceptions of Tesla and the VW group are looking at it for heavy freight over long distances.

The Rivian BEV truck horror story is a good example of trying to stick in more and more batteries in a negative feedback cycle to more around the ever increasing weight of the absurdity.

And FCEV would weigh far less for the job.

Don't fancy hydrogen much myself for maritime use, much prefering methanol, but it seems hydrogen is what is being installed with the Italians for instance in the process of sticking in 100 hydrogen fuelling stations at marinas for leisure craft..


For the Candela type systems you are only really substantially fighting the weight and drag of the boat to get it up on plane on the hydrofoils, after which energy consumption drops drastically to around the same as it would be doing at 4 knots or so, even though it is going much faster.

You certainly need to give it a lot of welly to get up to the point where it is foiling, so any system would need fairly substantial battery assistance to a hypothetical fuel cell set up.

I would imagine the weight limitations, if any, come in from the strength of the materials for the foils etc?

They are only just developing marinised fuel cells, so Candela has enough on its plate to think about building more of its very sucessful battery powered line in relatively small sizes.


“ And FCEV would weigh far less for the job.”
This is not true. Compressed H2 Tanks even using expensive carbon fiber are not light and take up a lot of space.

The Tesla Model Y BEV weighs the same as the Toyota Mirai FCEV, with a modest increase in range (330 miles vs 400 miles). They both cost over $50K.

Why do you think Daimler is looking at liquid H2.


@Gryf said:

'Why do you think Daimler is looking at liquid H2'

Because it is even more energy dense than gaseous, even 70bar, and as importantly saves volume as well as weight, important in a freight application,

That does not mean that even with gaseous hydrogen, which in an application such as leisure and light load carrying/towing such as the Rivian would be at 700bar, increments remotely as fast as batteries for more energy content. There are other trucking providers other than Daimler who are looking to gaseous hydrogen as 'good enough' without the hassles of liquifaction.

I have not easily tracked down recent figures or the latest stuff for improvements in weight since the Mirai/Nexo had there last update, but it is not even close enough to be important:

Here is the Rivian:

So you are getting ~140KWh for ~800kg

Here are the CF tanks for the Mirai/Nexo generation of fuel cell vehicles:

So ballpark we have 5kg or so of hydrogen for a 100kg tank

Of course for doubling the capacity in a cylindrical pressure vessel you do not necessarily double the weight, but forget about that,
So for 200kg of tank, you would get 10kg or so of hydrogen, and for 300kg 15kg

At 33KWh per kg that comes to 330KWh or 445KWh

Of course a fuel cell is not as efficient as a battery, but taking it at 50% you have 165Kwh useful or ~220KWh for the 300kg tank option.

As for anything remotely approaching the 800kg of the Rivian if used for a CF tank.......

You still need the weight of the fuel cell and ancillaries, and the the ancillary batteries, but it is clear that once you go to that sort of energy needed fuel cells are operating at an ever increasing advantage.

Your own comparison of the Tesla Model Y and the Mirai is for vehicles which are at the lower end of the scale, before the discrepancies really kick in.

But the primary reason for the poor sales of the Mirai were due to the lack of hydrogen stations, which is also why we don't have fuel cell pick ups.

I know which I would want for towing though.


This is a test comment from Typepad Support.

Roger Pham

Practically, I think that biomethane would be a better alternative for light-duty private vehicle for commuting than hydrogen and battery. A compressed natural gas tank requires 2.5 times lower pressure and 1/3 the volume of a compressed H2 tank for the same amount of energy, thus will cost and weigh 1/5 the cost and the weight of H2 and take up 1/3 the internal space.
Refill infrastructure for methane / natural gas is already established nation-wide, and can be very easily expanded further with much lower cost than for compressed H2. Natural gas is already available to every house and business.
We have to fast track renewable fuel because we have no time to wait for perfect solution, which may never come.

For long-haul trucks, train, planes, and ships, Liquid Hydrogen (LH2) will prove to be superior in term of low weight, space efficient, and rapid filling up.


Hi Roger

The attraction of hydrogen is that it is at least potentially more or less entirely free of GHG.
For methanol you still get shed loads of CO2 emitted.

For boats, at least big ones, it looks as though it may be possible to store it onboard and recyle it, but no one AFAIK sees anything like that happening for cars etc.

There is however some possibility of moving to hydride storage for hydrogen, with the redoubtable Professor Antonelli with his leading the way, with Quebec Hydro developing the same technology as a competitor:

'Kubagen's step-changing material uses Kubas binding to its patented transition metal-based Kubas Hydrogen Sponge (KHS-1) to give hydrogen storage systems which project four times the volumetric density of 700 bar incumbents at five times lower costs, making hydrogen fuel cells an attractive alternative to lithium battery technologies, especially for long haul and off grid applications.'

There are other possibilities also, although none so attractive AFAIK

Roger Pham

Biomethane made from the combination of waste biomass and green Hydrogen is also entirely free of GHG, although requiring processing from the raw biomass. This is desirable, however, because if the biomass is allow to rot, methane gas and CO2 would still be released into the air without the benefit of reduction in fossil fuel consumption. So, why not use the waste biomass in combination with green H2 to displace fossil fuel?
The plus side of biomethane over hydrogen is that biomethane uses the exact same infrastructure as natural gas, so no new infrastructure will be needed beside facilities for transforming the biomass into biomethane.

The attraction of Hydrogen is that it is very simple to use straight from the electrolyzer without further processing, for desert countries without sources of waste biomass. So, liquid Hydrogen will still be very valuable for big trucks, trains, ships, and planes whereby the massive weight reduction of LH2 will make a big impact in term of payload advantage, and the rapid fill-up and much lower energy cost of fill-up of LH2 in comparison to compressed H2.
Plus, LH2 is much easier to store in vast quantities at the terminals than compressed H2 that is far more costly and more dangerous to store in vast quantities.

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