Yamaha Hydrogen Engine Prototype at the Miami Boat Show

Yamaha Motor Corporation, U.S.A., unveiled the world’s first hydrogen-powered outboard prototype at the 2024 Miami International Boat Show.  The company plans on testing and refining the engine and fuel system later this year in an effort to determine its viability as a way of achieving carbon neutrality.

While Yamaha might be the first to make such an announcement in boating, they are hardly the first to experiment with hydrogen propulsion.   Many car manufacturers have dabbled in this area, and Toyota and Hundai currently sell hydrogen models.   Honda, BMW and Porshe plan to do the same in the near future.  Likewise, several major motorcycle manufactures are exploring this technology as well.

This got me wondering whether this is truly the next big thing or just another Segway or Google Glass. So I did a bit of digging into hydrogen propulsion to get a better understanding of how it works and the pros and cons vs. conventional engines.

What is Hydrogen Propulsion?

Diagram of the electrolysis process to split water into separate hydrogen and oxygen components

Electrolysis Process

Hydrogen is the most common element in our universe.  However, it is rarely found in pure form but is commonly bound to other elements to form things like water (H2O) and methane (CH4).  There are various methods to extract the pure hydrogen.  The most common method is called Steam Methane Reforming (SMR) which involves reacting natural gas with steam at high temperatures to extract the hydrogen.  An alternative approach, called electrolysis, uses an electric current that is passed through water to split out the separate Hydrogen and Oxygen components.  This method of production is more environmentally friendly but also far more expensive and so is seldom used today.

Regardless of how it is produced, the pure Hydrogen can be used for energy in one of two ways:

Fuel Cells

The hydrogen is stored in fuel cells that can be used like batteries to produce electricity to power an electric motor (similar to an Electric Vehicle).

Hydrogen Internal Combustion Engines (HICE)

The hydrogen is used for combustion instead of gas or diesel in an engine that closely resembles a standard internal combustion engine.  This is the approach that Yamaha showcased at the Miami Boat Show.

Of the two types, it seems that Fuel Cell hydrogen propulsion is about twice as efficient as hydrogen internal combustion engines.  That means you could travel twice as far or spend half as much on fuel.  For this reason, the rationale for using hydrogen in an ICE isn’t clear to me other than the familiarity and the capital/tooling already invested in combustion engines by some manufacturers.

Advantages of Hydrogen

In comparison to fossil fuels, hydrogen does have certain advantages as a fuel source:

  • It is abundant – that is, after you extract it from a source like water.
  • It is renewable – it is not something that we have to worry about running out of.
  • It is cleaner to “consume” than gas or diesel.  For fuel cell hydrogen engines, the only by-product or emission is water vapor.  With hydrogen internal combustion engines, Nitrous Oxide (NOx) is also produced from the heat generated during the combustion process which is not great for the environment.  But you don’t get the Carbon Dioxide (in addition to NOx) that is emitted by gas or diesel engines.
  • You can refuel quickly – just like a gasoline engine IF you can find a hydrogen fuel station (more on this later). No need to wait several hours to recharge like a Battery Electric Vehicle (BEV).

Disadvantages of Hydrogen

However, there are some major limitations of using hydrogen as a fuel source (or, as some would say, a fuel carrier) at the present time, including:

  • It is “dirty” to produce in most cases. There are different methods of producing hydrogen that are denoted by various colors.  Grey hydrogen uses natural gas in a process called Steam Methane Reforming (SMR) as noted earlier.  However, producing hydrogen in this way also creates Carbon Dioxide which is harmful to the environment.  But, because it is the most economical method at present, over 90% of hydrogen is produced in this fashion.

Blue hydrogen is similar except it uses a process to capture and store the CO2 that is emitted (although studies have shown that a fairly high proportion still escapes into the atmosphere).

Green hydrogen using energy from renewable resources such as wind and solar to split water into its separate hydrogen and oxygen components through a process called electrolysis.  While this is the most environmentally-friendly method, it is also the most costly and difficult to scale.

Regardless of the method to produce the hydrogen, there are additional pollutants resulting from the transportation of it to a refueling station – just as you do with gas or diesel.  Note that you do not have this issue with electric energy which is transmitted through cables.

  • It is more expensive. At present, hydrogen is approximately twice as expensive as gasoline on a per mile basis.
  • It takes up a lot of space. Hydrogen, which is typically used in a gaseous form, has a much lower volumetric energy density than (liquid) gasoline.  To address this, it is often stored in pressurized cannisters (approximately 10,000 PSI) which can also introduce safety concerns.  Though some car manufacturers have experimented with using hydrogen in liquid form, this creates a slew of other challenges because hydrogen has a very low boiling point (-423F, -253C) and will revert back to a gaseous form at temperatures above this.
  • hydrogen stationIt is not readily available.  While EV owners have been frustrated with the limited availability of charging stations, hydrogen refueling locations are almost non-existent.  In response to this, the Biden administration announced plans in October of 2023 for a $7 Billion investment to develop seven regional “Clean Hydrogen Hubs”.  However, these hubs will likely be used for commercial and agricultural applications and so will have little impact on availability for consumer/recreational use.


As with Electric propulsion, the use of Hydrogen as a fuel source for boating has some serious limitations at the present time.  Perhaps the most fundamental weakness is that it doesn’t really solve the emissions issue due to weaknesses with the production process.  While this may improve over time as more “Green Hydrogen” production facilities are developed, this will take considerable time as have all “green energy” solutions to-date.

Nonetheless, I applaud Yamaha for taking the risk to innovate.  I doubt that the company expects to launch a viable, hydrogen-powered, internal combustion engine for recreational use anytime soon.  But they likely will learn a great deal about the potential benefits and pitfalls of this fuel source through the process which could lead to some other breakthroughs down the road.

However, if you are in the market for a new boat, I would not recommend holding up your plans until this next generation of outboards arrives.  You might be waiting a very long time.


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Jerry Mona - BoaterInput

About the author

Jerry Mona is an avid boater and angler and long-time boating industry insider. With over three decades of experience, he is often considered to be the leading research expert with boaters and has helped numerous manufacturers and trade associations to understand the needs, wants, attitudes and behaviors of boaters. He now shares many of his insights about boats and boaters for free on his BoaterInput.com website.

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