Hybrid boat: The benefits of converting to an additional electric motor - and what not
BOOTE
· 26.03.2026
A text by Andreas Mengen
The maiden voyage of our Neon 910 "Luna M", which has been converted into a hybrid boat, begins with a launch in the harbour of YCRM Koblenz. To start with, we use the 150 hp Mercury - better safe than sorry. In calm conditions, we head out onto the Moselle. There, the electric motor is to show what it can do. The combustion engine is run up to minimise water resistance. But then the disappointment: even with the most foresighted steering, the boat cannot be kept on course with the 4.4 kW Torqeedo alone. The semi-planing hull of the Neon, which is even equipped with a small longitudinal keel, sails in a serpentine line.
We start thinking about increasing the shaft surface of the electric motor to create a stabilising rudder blade effect. In a mixture of despair and helplessness, we finally lower the combustion engine again. And lo and behold: "Luna M" drives perfectly straight ahead. The first logical conclusion is that the stabilising rudder blade effect of the combustion engine cannot be dispensed with. It must remain in the water even when travelling purely electrically.
Fast ride
The driving performance under electric drive alone is a maximum of eight kilometres per hour, which is above expectations for a motorboat weighing around 4.5 tonnes. The combustion engine is disengaged and the propeller turns freely. At its peak, the Cruise 4.0 consumes 4,400 watts of power and pushes water out the stern with a powerful whirring sound. The batteries last for around an hour. With just 1,500 watts, it can still reach speeds of over five kilometres per hour - definitely enough for water touring on small rivers and lakes.
At this moderate speed, we can cover a good twelve kilometres on one battery charge. The reduced power is also sufficient when travelling downhill on flowing water, which also increases the range here.
However, a look at the performance figures also shows that powering the electric motor solely via the on-board photovoltaic (PV) system while travelling is not enough. At best, it produces a good 300 watts. This is less than the 1,500 watts of power consumption required for cruising under electric drive. Nevertheless, the PV acts as a range extender when the lithium-ion batteries are recharged during the journey with 200 watts via the chargers. Emptying the batteries is noticeably delayed. Of course, it is good that the PV also works when the vehicle is stationary and recharges all the batteries on board. For longer stopovers of two days or more, you can therefore top up your batteries free of charge.
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Of course, the safer option is to use shore power in the harbour overnight. Then you charge with 600 watts and always start the morning with full batteries. On a river trip down to the valley with a strong current of one to two knots, we covered 50 kilometres purely electrically in two days. The second realisation is therefore: under ideal conditions, even longer distances can be covered quite comfortably without the combustion engine.
Good manoeuvrability
Another surprise is the good manoeuvrability under electric drive alone. As described in the first part, the Torqeedo is also operated via the hydraulic control of the combustion engine thanks to some modifications. Both motors therefore move in parallel, which ensures a good rudder effect. The electric motor also has sufficient thrust for starting and stopping. In conjunction with the Neon's standard bow thruster, mooring and unmooring at the jetty or in the lock is therefore safe, even without the combustion engine.
Once you have acquired a taste for it, you will want to drive purely electrically whenever conditions allow. You should always keep an eye on power consumption, power generation and the charge level of the batteries. The consumption can be read on the remote throttle display and the PV output on the remote display. What is still missing is the charge level of the lithium-ion batteries. The use of a shunt with Bluetooth function is recommended. Then you can see the current voltage on your smartphone and don't have to stick your head deep into the back box to read it.
Of course, the range could be significantly increased if we doubled the battery capacity, for example. But apart from the costs, the question is whether this is worthwhile. It depends very much on how the electric drive is used: How far away are the frequently travelled destinations, how often are distances covered against the current? If you want to travel uphill at five km/h on the Rhine, for example, even double the battery capacity won't help - you're almost standing still anyway. And whether the batteries last for one or two hours is ultimately irrelevant. So there's no getting round the combustion engine here. The realisation: a lot does not always help a lot.
Instead, it turns out that the advantages of both drives complement each other perfectly. There are conditions under which the electric motor does a great job on its own. But at a certain point, it is time to utilise the advantages of the combustion engine.
Flying change
In contrast to the combustion engine, the Torqeedo must not remain permanently in the water. If the worst comes to the worst, it must even be possible to put it down on the stern platform in the blink of an eye. For example, if you find yourself in a situation where more power is needed or a higher speed is required. The 150 hp Mercury takes the semi-glider to over 30 km/h. An electric drive could be damaged by the high water resistance.
Switching from electric to petrol on the "Luna M" takes less than 30 seconds. All you have to do is loosen two clamping screws by hand, lift the Torqeedo out of the water, swivel it sideways and put it down in the horizontal storage position. That's it. Data and power cables stay where they are. The whole thing works just as quickly in reverse.
If you had to get the electric motor out of the back box every time, carry it to its place, attach it and connect it, you would probably think three times about whether it was worth the effort. The reverse is just as important: in tricky situations, the electric motor must be able to disappear quickly and the combustion engine can take over.
However, storing the electric motor on the bathing platform is also a disadvantage. Thieves are presented with this expensive item on a silver platter, especially if the boat is moored with the stern facing the pier. There is a chain lock, but it is certainly not an insurmountable obstacle. That's why the "Luna M" now has a stern tarpaulin. This not only keeps out prying eyes, but also ducks.
The settlement
The question remains as to whether the hybrid concept pays off. What about the energy costs during operation, i.e. the running costs per kilometre? Let's take a look at a journey at water travelling speed.
Let's start with the combustion engine: A comfortable and maximum fuel-efficient canal trip measured in litres of petrol per kilometre is achieved at 7 to 8 km/h. The Mercury then consumes just under 0.4 litres. That would be 40 litres per 100 kilometres. You currently pay around 2 euros for a litre of petrol at the boat filling station. That's 80 cents for one kilometre.
With the Torqeedo, we assume a power consumption of 2 kW, whereby we are then travelling at 6 km/h. If 5 kWh are available in the batteries, you can drive for two and a half hours and cover 15 kilometres. The energy consumption for 6 kilometres, which we cover in one hour, is 2 kWh, so 0.33 kWh for one kilometre.
If we assume a price of 30 cents per kWh, then we are driving at 10 cents per kilometre - which is unbeatably cheap. The better we manage to get our own PV power into the batteries, the lower the value becomes. Converted to an hour, you can drive a boat for an hour for 60 cents. This is indeed an extremely low figure and, from a cost perspective, is almost like sailing - albeit with significant restrictions in terms of speed and distance. Nevertheless, the 6 euros per hour for a combustion engine is expensive fun in comparison.
The bottom line
The electric motor can score points at moderate speeds, because even a small amount of energy is enough to get going. Only this energy is absorbed and must be paid for. The combustion engine, on the other hand, due to its technical design, cannot fall below a certain energy hunger, no matter how restrained the driving style. The ratio of energy absorbed and energy put into the water is significantly worse. The engine runs in an unfavourable speed range, a relatively large proportion is dissipated as heat and wasted.
The petrol engine really comes into its own when the going gets tough. Then the electric motor can pack it in straight away. What's more, we can travel around 400 kilometres or more (on a hike) with just 220 litres of petrol on board. The electric motor runs out of juice much sooner.
The final conclusion is that the hybrid solution on the "Luna M" is a complete success for us. If it is clear that you only want to and can only use an electric motor as an additional drive solution under suitable conditions, then the disadvantages are minor, but the advantages are huge. It's amazing how often a small drive is sufficient in everyday life on board.
And who knows, thanks to advancing technology, it may even be possible one day to completely replace the large combustion engine with a more powerful electric counterpart. We are curious.
Combustion engine vs. electric motor: comparative figures
Interview: About the performance potential of PV systems on yachts
BOOTE: The Neon 910 presented in the article has a PV system from SunWare. What components does it consist of?
Manuel Jaeger: The solar system on the "Luna M" comprises seven semi-flexible SW20 series marine solar modules with different dimensions and outputs, from 30 to 120 watts peak power (Wp). Together they deliver 424 Wp. The power is fed directly into the twelve-volt on-board power supply via a Fox 320 solar charge controller. The charge controller can split the power flexibly between two different batteries, such as the consumer and starter batteries. A Fox MD1 remote display was also installed. It can be positioned independently of the charge controller, for example in the navigation corner.
What is special about SunWare solar modules?
They have been specially developed for marine applications. They are optimally protected against salt water, high UV radiation, temperature fluctuations and vibrations. What's more, they are only a few millimetres thick and can be mounted flat on the deck. They are screwed or glued in place so that no additional brackets are required. This has the advantage that no water or dirt collects under the modules. And: the deck area can still be walked on, as the modules can be walked on.
How large are solar systems on yachts usually dimensioned?
For small boats, 20 to 50 Wp is enough to maintain the charge. For larger yachts or yachts equipped for longer trips, 300 Wp solar power and more are not uncommon. As a rule, this is intended to support the on-board power supply by constantly recharging.
And what characterises the solar system on the Neon 910?
There are even 424 Wp installed on board the Neon 910. This is a particularly powerful system for a boat of this size. This is due to the fact that an alternative electric drive is to be supported here in addition to the on-board power supply. Completely self-sufficient electric driving is therefore not possible. However, a particularly quiet journey can be enjoyed on individual sections of the journey. The solar system on the Neon 910 is therefore a prime example of how modern and pioneering technology can be used on pleasure craft.
