The discussion about electric engines in sailboat has started and some boat yards are beginning to equip their Â*(bigger) yachts with a hyprid engine system or (on smaller units and inshore sailboats) with an electric engine. The number of companies Â*in Europe, offering packages of complete engine systems is growing and that makes it interesting for owners of existing yachts to think about an electric engine when the old Diesel has to be replaced.
Our Volvo MD2B (25hp/18,3kw) was 36 years old. It was still running, but it showed clear signs of age - the stability of temperatur und rpm was decreasing and it was getting hard to get spare parts.
Â*02 alter Diesel.JPG
After a long process of looking at the pros and cons we finally decided, that an electric propulsion system fits to the boat and â€“ maybe even more important - to our â€žmotoring habits".
Centurion 32, a former IOR-half ton â€“ therefor good sailing performance
weight of about 5,5 metric tons (fully equipped)
so far an 18,3kw diesel engine, with a real power potential of 7,3kw (the rest was heat and noise) due to an (estimated) efficiency ofÂ*Â*40%
The motoring habits:
the main use of the engine is to get in and out of harbours, marinas and crowded anchorages
under rare occasions we use the engine to make the last miles into the harbour after the wind died and if it does not make sence to stay out at night
we never motor against wrong tides, winds or severe calms
if necessary, we look for a new destination instead ofÂ*Â*starting the engine to meet once set schedules
we love to sailÂ*Â*at 2 to 3kn even under light wind conditions and if we use the engine a speed of not more than 4 knots is fine
we never use the engine for extended passage making
in the years of weekend sailing andÂ*Â*sailing vacation the engine runs about 40 to 50 hours in a sailing season (April to October)
during periods of living aboard we used 90 litres of Diesel in a year on two occasions (Northern Europe, Caribbean and back in 15 months and between Northern Europe and Gibraltar/Marocco in 12 months )
during offshore / ocean sailing we never used the engine for passage making. (Sooner or later, every calm ends â€“ it's just a matter of time and patience and good books...) Â*The engine was never used for battery charging, which is done by shore power if available or otherwise by wind generator and solar panel.
The new electric motor system had to meet the following needs:Â*
- a power of about 10kw should be sufficient, creating a realistic power potential of 9kw (at Â*an efficiency of 90%).
- It should be poweful enough to move around savely in crowded marinas and to keep away from any dangers in tidal waters
- the new system including the batteries should equal the weight of the Diesel engine, gear box, starter battery and 60 litres of fuel.
- all components (especially all batteries) should find their place in the engine compartment to make sure that the trim is not influenced negatively.
- a driving range of about 15 to 20 nautical miles (as a relistic half distance between two ports in the northern European waters we sail during normal weekend / vacation settings, if not sailing over night) under engine
- we wanted to install the system ourselves â€“ therefor we wanted to keep the existing traditional prop shaft arrangement
- under sails the motor should function as a generator
- the system should work on Â*12/24V and not on three-phase-curent, as bigger units use. Â*
While looking around searching for experience and manufacturers we soon found out that a sister ship, driven by electric power was already on the water in Norway:Â*Sy Ren Glede
(and click on Last ned beskrivelse
for a the description). This led us to the swedish manufacturer of innovative yacht equipment OzMarine
OZMarineÂ*Â*specializes on electric motors for sailing yachts and their package includes all parts to run the system, including the motor itself, made up by two electric motors set in line to drive the axle, the folding prop, axle, axle sealant, axle bearing, motor controller, charging electronic to use the motor as a generator, complete shore power system with 230VA/C battery charger and the battery control unit and the cabeling.Â*
Installation was easy and astonishingly fast.Â*
We removed the old engine (with the only outside help to hoist out the heavy old Diesel engine), cut back the old engine mount and rebuilt it as a fibreglass/wood-structure to fit the new engine.
Aligning the engine was easy, as the two el-motors are placed in a stainless steel frame that swings around a lateral axis. To define the correct elevation of the engine in relation to the prop shaft, stainless steel plates can be placed under the engine frame and finally the bolts that hold the engine to the mount are a little less in diameter than the holes in the engine frame, giving a little flexibility to work around the vertical axis.Â*Â*And as the whole engine only weighs 32 kg it is no problem at all to successfully install the engine all by yourself!
04 Motorfundament raus.JPG
12 Batterien eingebaut.JPG
We installed six VRLA-Gel batteries (100Ah)
- to get the necessary weight to replace the Diesel engine,
- to place them in the engine compartment and not anywhere else unter the bunks to maintain the trim and to keep the cabeling short,
- to reach a range under engine of about 20nm without draining the batteries more that 50% (this is not much but it perfectly well fits into our traditional motoring habits)Â*
First trials met our expectations.Â*
6 months in tidal waters, out of that one month cruising, at night in marinas using shore power. On one calm day 23nm over ground, going with the tide under engine, otherwise weekend sailing.Â*
- the engine reacts powerful and fast â€“ good for crowded marinas and anchorages.
- at a "cruising speed" of almost 4 knots under calm conditions (which is perfectly enough for us) it consumes about 60A . That gives a range of about 18 nm at a consumption of 300Ah â€“ using Â*50% of the total battery - capacity.Â*
- under full speed (at 24V) the speed is 5,8 knots, which can be maintained for nearly 40 minutes. Enough time and speed to escape from risky situations, without abusing the batteries
- normal motoring in and out of a marina can be done with a power consumtion of 12 to 16 Ah.
- charging under sail is possible with up to 10A under ideal conditions (wind generator, solar panel and using the engine as a generator).
- If shore power is available the charging is done by a 50A-automatic charger.
But for two reasons we decided to complete the system with a Honda i10 Generator:
for the most unusual case of being in the need to use the engine for more than the 18 nm, we can take the generator to recharge during motoring: with an input of 50A and a consumtion of 60A we will be able to extend the range by the factor 6, that makes 108 nm under engine. We NEVER motored this far in our whole sailing life! So, the chance that we actually have to use the Honda for motoring (in a "hybrid"-configuration) will be almost zero.
13 Windgen Solarkoll.JPG
As we plan to do more extended sailing outside European waters and thus far away from 230V shore power, the generator will be the only source to guarantee the possibility of intelligent and complete charging (bulk at 14,4V at a maximum current; absorbing at 14,4V at a gradually decreasing current and finally at floating charge at 13,8V). Other sources on board (wind gen, two solar panels and engine functioning as generator) will charge the batteries, but only to the level of 13,8V.
The new feeling of motoring:Â*
In former times we experienced the ideal situation of sailing and the necessity of motoring. Now the motoring is the extension of light wind sailing without sails: No noise, no diesel fume.
And as the reaction of the el-motor is faster and more poweful, it is much easier (and safer) to move around in crowded marinas. And all that without any noise!Â*
And just these days we completed the first battery-cycle (646Ah used) after 350 days of use with 8 months in the water, regular weekend sailing and a 4 week sailing vacation.
The two extremes of the reactions of fellow sailors:
- very much interested as this will be the future on our boats
- no way, I need my strong diesel to work against all tides, winds and eventualities and new engine should be stronger as the old one...
How do we think after the first year?
- like explorers in new territoryÂ*
- No real engine any more: we sail further in into the harbours, marinas and on anchorages, if the traffic permits
- feeling a little anxious when thinking of sailing long distances again in the future without our traditional Diesel engine (but in the 60ies and 70ies of the last century the blue water sailors did the same with small or no engines and also made it far beyound the horizons!)