From August, Honda started demonstration trials in Matsue City, Shimane Prefecture for prototypes of electric propulsion designed for small watercraft. The trials verify the commercial quality of electric propulsion prototypes mounted on Horikawa sightseeing boats that circulate on the moat surrounding the city’s national treasure, Matsue Castle.

The founder, Soichiro Honda had long envisioned carbon neutrality on water.
This article features Honda’s challenges that have set off for making a reality of this wish.

Aiming for zero environmental impact, Honda established a fundamental concept of the ‘Triple Action to ZERO’ in 2021, which integrates three elements, namely “carbon neutrality”, “clean energy”, and “resource circulation”, into one. Honda’s objectives include leading efforts in 2030 to realize a carbon-free society, and achieving net zero CO2 emissions by 2050.

In November 2021, Marine Business Division released a concept model for the electric propulsion toward realization of carbon neutrality. The electric propulsion is basically an electric outboard motor driven by a battery. 　Honda calls it a “propulsion unit” for its future application not only to traditional outboard motors mounted to the transom of a boat, but also to different types of power units.

During a search for a demonstration trial subject to test these electric propulsion prototypes designed for small watercraft, Honda received an offer from Matsue City, Shimane Prefecture of electrification of the city’s Horikawa sightseeing boats, which are equipped with Honda’s four-stroke engine, BF9.9. Matsue City’s proactive efforts toward carbon-neutral tourism coincided with Honda’s approach toward the global environment, resulting in launch of the demonstration trials.

How many outboard motors are currently sold in the world, and what kind of motors are they? The global market size for outboard motors is about 0.9 million units (data source as of 2022: Honda), of which approximately 80% is accounted for by four-stroke engines, and the remaining 20% accounted for by two-stroke engines.

A four-stroke engine requires two reciprocating movements of the piston to complete a cycle of four steps, intake, compression, combustion, and exhaust, whereas a two-stroke engine needs one reciprocating movement of the piston to perform two steps of intake and compression, and combustion and exhaust. While the two-stroke engine is simpler in design, less expensive, and lighter in weight, it has a disadvantage of discharging not only exhaust into the air but also unburned oil into the water due to its combustion mechanism using a mixture of gasoline and oil. Compared to the two-stroke engine, the four-stroke engine emits less exhaust.

The world’s biggest outboard motor market is North America with as many as 420 thousand units, followed by Europe where about 200 thousand units are sold. While approximately 35 thousand outboard motors are traded in China, Japan buys about 13 thousand units. The mainstream of outboard motors are four-stroke engines in North America, Europe, and Japan; on the other hand, two-stroke engines are still in the majority in Latin America, other Asian countries, the Middle East, and Africa.

Based on the philosophy of the founder, Soichiro Honda that "watercraft should not pollute the water”, Honda has been particular about developing four-stroke outboard motors of less environmental impact. Overcoming disadvantages of four-stroke engines such as numerous components, heavy weight and high cost, with high ambitions and technologies, in 1964 Honda forayed into the outboard motor market almost monopolized by two-stroke engines with its first four-stroke outboard motor, GB30. Since then, Honda has been consistently producing only four-stroke outboard motors.

Nowadays, Honda boasts an extensive lineup of outboard motors ranging from 2- to 250-horsepower models. In the fiscal year of 2022, the sales reached to as many as 61 thousand units, which are mounted on watercraft of different purposes including pleasure fishing boats, commercial fishing craft, excursion ships, cruisers, coast guard boats, etc.

The biggest advantages of electric propulsion are zero CO2 emission, low noise, and low vibration, similar to four-wheel and two-wheel EVs.

Furthermore, the electric propulsion prototype for the trials is equipped with a detachable portable battery, Honda Mobile Power Pack e: which has been already in use on Honda’s electric motorcycles. Swappable batteries have facilitated a continuous boat ride with no wait time for battery recharge.

Horikawa sightseeing boats carry Honda’s four-stroke engine, the BF9.9 (whose 9.9-horsepower is almost equivalent to 7.4 kW). If all the boats were electrified, 47 tons of CO2 could be reduced annually. Additionally, the noise level is about 5db less than before when the boat cruises at a constant speed (5 km/h), while vibration is cut by approximately 60%. On a boat with a conventional engine, a boatman needed a microphone and speaker for guiding, but on a boat with electric propulsion it is so quiet that conversation on board no longer requires any audio device. Producing no unpleasant noise or odor, electric propulsion contributes not only to the environment, but also passenger- and local community-friendly sightseeing boat tours.

This interview features Kurama Fukuda, General Manager of Marine Business Division, Power Products Business Unit, Motorcycle and Power Products Operations’ aspirations toward carbon neutrality on water, who took on the demonstration trials on electric propulsion prototypes mounted on Horikawa sightseeing boats.