With the Vetus Hybrid Kit, boat owners do not need to replace the entire propulsion system for short electric journeys. The system, marketed under the name M2HSET, is designed for the M2.13 and M2.18 two-cylinder diesel engines. According to the manufacturer, it is suitable both for retrofitting compatible systems and for new builds.
This approach is particularly of interest to boat owners who wish to continue using their existing diesel engine but would like to avoid its noise and exhaust fumes whilst moored or on short journeys. The combustion engine remains responsible for longer journeys. The kit is therefore a supplement to the existing powertrain, not a complete replacement with a high-performance electric motor.
Up to 2.1 kilowatts for slow driving
At its heart is a liquid-cooled permanent magnet motor with an operating voltage of 24 volts. Vetus states a maximum electrical power output of 2.1 kilowatts and a maximum torque of 17 newton-metres. The electric motor is connected to the propeller shaft via a V-ribbed belt and a specially adapted pulley.
By way of comparison: The M2.13 According to Vetus, it produces 8.8 kilowatts or 12 PS, the M2.18 amounts to 11.8 kilowatts or 16 PS. The maximum power output of the electric motor is therefore, in theoretical terms, just under a quarter of the rated power of the smaller diesel engine and just under a fifth of the rated power of the larger one. Electric mode is intended for slow driving and manoeuvring. As soon as more power or a longer journey is required, the vehicle switches to diesel mode.
Technical specifications of the M2HSET
| Characteristic | Manufacturer's specifications |
| Compatible diesel engines | Vetus M2.13 and M2.18 |
| Electric motor | Permanent magnet motor, liquid-cooled |
| Operating voltage | 24 V |
| Maximum electrical output power | 2.1 kW |
| Maximum torque | 17 Nm |
| Maximum engine speed | 1,600 rpm |
| Charging current in diesel mode | up to 30 A |
| Connection to the propeller shaft | V-ribbed belt |
No generator operation: the propeller must be turning for recharging to take place.
The belt drive for the electric motor is located on the output side of the reversing gearbox. This enables the electric motor to drive the propeller shaft whilst the diesel engine is disengaged, independently of the internal combustion engine. For generator operation, however, the opposite applies: the propeller shaft must be rotating so that it drives the electric motor via the belt. Vetus explicitly describes recharging via the rotating propeller shaft during diesel operation.
With this configuration, it is not possible to run the generator in stationary mode whilst at anchor. The hybrid system’s charging function is therefore not equivalent to an auxiliary alternator driven directly by the diesel engine. Vetus makes no mention of a charging function whilst under sail.
The charging capacity also remains modest: the manufacturer states up to 30 amperes. At a nominal voltage of 24 volts, this equates to 720 watts. Recharging is an additional function whilst driving on the diesel engine; it is not a substitute for a high-performance charging system.
Anyone who, above all, needs more charging current and would also like to charge the battery using the diesel engine whilst at anchor may wish to consider an auxiliary alternator instead. This is driven directly by the engine and is therefore not reliant on the rotation of the propeller shaft. The YACHT article explains the options offered by high-performance regulators, a separate alternator and water-cooled systems: Auxiliary alternators and the charging of lithium batteries. Whether such a solution is suitable for a small two-cylinder engine depends, amongst other things, on power requirements, installation space and the availability of a belt drive.
In the Vetus concept, both the diesel engine and the electric motor can drive the same propeller shaft. The differences between this and purely electric and other hybrid solutions are explained by the Overview of propulsion systems for yachts based on their respective advantages and disadvantages.
Retrofitting for two M-Line engines
For compatible vessels, it should be possible to reuse the existing engine mounts and propeller shaft. This means less work is required compared with a complete propulsion system replacement. However, the kit is not a universal retrofit solution for any diesel engine. Vetus specifically mentions the two M-Line two-cylinder engines first. The Technical product page for the M2HSET brings together the specifications and the accompanying installation instructions.
Vetus has not yet announced a price or a specific delivery date for Germany.
Book recommendation
Electric mobility on the water explains the technical principles behind electric boat propulsion systems and covers fully electric systems, hybrid solutions and fuel cells. Specific case studies illustrate the conversion of sailing boats and motorboats. The book also includes guidance on installation, operation and maintenance, as well as calculations to assess cost-effectiveness.
Would you fit such a system as a retrofit, so as to carry out harbour manoeuvres without using diesel whilst retaining the range of the diesel engine for longer journeys?
Hauke Schmidt
Test & Technology editor