#TBT: Accumot – granddaddy of electric outboard

Kevin Desmond’s definitive book ‘Electric Boats and Ships: A History” (buy on Amazon)  lives up to its name, covering 180 years worth of electric and clean marine propulsion from the first electrically powered boat in 1837 right up to the book’s publication in 2017.

Along the way hundreds of electric motor and battery combinations have been tried, from the 550 kg / 1212 lb Morritz Immisch motor with 24 accumulators to the world’s first solar boat, Alan Freeman’s 2.5m / 8ft catamaran with a power output of 1.3 watts.

Not all of the e-boat dreamers and designers have been this far outside the mainstream, though, and the Preinerstorfers of Austria – Franz, Otto and Herman – should probably be recognized as putting together the first electric outboards as we know them today. In fact, in many ways their Accumot motors (not related to the Aquamot company of today) were far ahead of their time and their innovative designs have inspired some of today’s most prominent manufacturers.

Invented electric outboards as we know them today

From Electric Boats and Ships: A History:

Franz, Otto and Hermann ran an electrical and radio sales and repair business in Gmunden. Franz and Otto were highly intelligent and interested in everything technical: Franz was almost a genius. He had studied both music and painting in Vienna, creating fine canvasses and composing for organ and violin concertos. The brothers invented various technical things: an optical arrangement using a system of rotating perforated discs for color photographic toning, both still and moving images; a wireless radio for Gmunden, Gmunden’s Cable One TV. They even developed a prototype color television.

Hermann, the youngest brother, was added as an apprentice and so got a very good technical training in an environment always looking for the latest technical and physical achievements.

The brothers’ electric boat adventures began in 1947 when they took a Siemens & Halske motor and rebuilt it as a 200 watt, 24 volt electric vertical transmission outboard for use in a boat on the local lake.

Along the way they supplied the motors for the boats in the underground grottoes of Vienna’s famous Seagrotte and the Caves of Han in Belgium, the Tivoli Gardens and Six Flags Amusements parks, not to mention thousands of dinghies, runabouts and sailboats.

a man in a small boat in the 1950s testdriving a motorTheir first test engines were above water motors with an output of about 200–250W that used components from truck generators. The motors were powered by 12 volt car batteries, but since there was no practical way to recharge them for a boat, they brothers designed their own self regulating charger with tube rectifiers. They realized it was a good business proposition to sell the chargers all matched up with the different motors and so introduced a package plan. In 1955 they improved on the system and were one of the first manufacturers to produce silicon rectifier chargers.

1955 Fantom model put the motor under the water

The new chargers were introduced with the new “Fantom” outboard: a 24-volt, 300-watt unit where the motor went UNDERwater not only to take advantage of the cooling capabilities, but also to increase effective power by taking away the need for a gear/transmission system to transfer the energy from motor to propeller.

two electric outboard motors - one has a protective ring around the propellerIn 1958 they boosted performance with a larger motor in a more bulbous case – the Turbo – which came in 30V/1kW and 36V/1.6kW models. It also introduced a protective ring around the propeller and motor casing.

Then they started looking at going the other way and wondered about a smaller motor to respond to demand from local sport fishermen. So they came up with the the world’s first practical trolling motor. The Minimot was a lightweight, easy-to-use 12-volt 180-watt motor with a pull switch in the machine head.

In 1960, Volvo Penta came up with their “Aquamatic” sterndrive, an inboard engine powering an outboard leg. Accumot Accumot responded with an electric 2 kW similar configuration and then a 1.5 kW in 1970.

Systems and motors have run for decades

For the Tivoli Gardens in Copenhagen, Accumot developed the first electric pod propulsion system for the park’s visitors to drive small boats around the Dragon Boat Lake. The accompanying recharging system enabled the boats to essentially run 8 hours a day with almost zero down time, and remained in operation at the park for decades.

electric outboards for sale on ebayAside from their remarkable series of innovations and responses, the continuing legacy of Accumot is the enduring quality and durability of the motors.

Although Accumot sadly closed its doors in 2006, literally thousands of their devices are still in use today and a quick Google search will show them up for sale on eBay and other European selling sites.

The other enduring legacy is that when looking at many of today’s electric motors and outboards, it is easy to spot the influence of Franz, Otto and Herman Preinerstorfer.

This Throwback Thursday touches on only a few of the highlights of Accumot. Electric Boats and Ships: A History has many more details about Accumot and the company’s influence. The last word for today comes from Hermann Preinerstorfer, in an interview with Kevin Desmond:

Leading up to the closing of the family business it was still making great technical strides by combining electronics with neodymium permanent magnet AC motors. But Preinerstorfer decided to take a well-earned retirement and see more of his family. “Over the years, the outboards made by our Accumot family business were copied. It was always a waste of time to take such copyright infringements to court. We always preferred to stay ahead by working on new projects.”

Historical pictures courtesy the Preinerstorfer family via Kevin Desmond

Click »» here to read some of the other Throwback Thursdays of electric boat history.

Electric Boats and Ships: A History
Available from Amazon, including Kindle

Amazon Customer Review: “Desmond’s new book leaves no doubt that electrically powered vehicles are already a fixture on the firmament of propulsion and will continue to be so for the foreseeable future. Well illustrated, meticulously written and researched, this book is a guaranteed ‘must’ on the bookshelves of all who have interest in this subject.


DISCLOSURE: The excerpts from Electric Boats and Ships: A History have been provided by Mr. Desmond and the book’s publishers at the request of Plugboats. Plugboats receives a standard Amazon affiliate commission for any copies purchased through the links on this site.

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