View Full Version : Arens Motorenbau, Romain-Roland Str. 14-24, 13089 Berlin

Smokin' Joe
09-17-2011, 06:10 PM
I became curious several years go when I saw the Portage Bay website with nice pictures of three Arens alky burners. I emailed Holger Arens in Berlin in Jan. 2009 in English and asked could we visit his factory sometime, the ground being that our (then 17 yr. old son Hans) wanted to study mechanical engineering. We travel from Austria to a NE German island every summer so the visit would be easy. Arens wrote back using an internet Geman-English translation program and said 'yes'. Since he grew up in east Germany his 2nd language is Russian. As usually happens, the visit was delayed. We got motivated last Aug. because Hans (May Fly III) enters engineering school (Maschinenbau) in Vienna in Oct.

On 12 Aug. I picked up Hans at Berlin Gesundbrunnen Bahnhof (train station). We navigated into NE Berlin in our 1997 Ford Contour (shipped to Bremmerhaven in 2000) via our Garmin GPS. We met Holger Arens and he first told us the history of their outboard manufacturing.

Holger Arens’ father raced hydros in East Germany as early as 1955. Holger hnimself built his first outboard in 1986. Son Lars works with his father, both have a Maschinenbau degree. In 1985 Holger and his father knew of König but could not buy parts in The West because the Reichsmark, the East German currency, had no foreign exchange value. They had to make everything. We saw no example of the motors of that era. Arens told us that he raced hydros until 1991, then quit. Either then or later, he said in German ‘One weekend of racing, one death’. Peter König later also emphasized the deaths in hydro racing in Germany. Arens made racing motors (125, 250 and 500 cc) 2001-2006, then quit. I asked about props and he mentioned Wald (not Dewald). Wald, an east German, lived nearby and Arens offered to introduce us.

Sometime during 2001-2006 Arens traveled to America to promote his motors. The 2001-2006 motors had v-block reeds with Rotax cylinders and pistons. They made their own crankshafts and built a König-style gearcase with Swedish gears. The reason that Arens quit was the Italian manufacturers, e.g. Rossi. The market is too small for several alky motor companies.

Arens later took us downstairs past their metal fabrication section into the outboard plant. On the way I saw a small sort of Mod-VP style tunnel with safety cell, presumably for the 500cc class. The bottom has a center pad between the sponsons. Arens said that this is the sort of race boat that is now approved in Europe.

One of the 2001-2006 250cc motors stood on a stand minus carbs and expansion chambers. Arens had already told us of their new project, two Boxer rotary valve outboards for sport boats. Both models are de-tuned racing powerheads. The smaller motor is 250cc (about 15 c.i.) with two cylinders and should develop 30 hp at 6000-7000 RPM. We saw two such powerheads but were asked please not to take pictures. The powerhead currently developes 70 hp at 9000 RPM. One was hooked up to expansion chambers (feeding into a car muffler, with the pipe feeding outside the building) and a dyno. The dyno was an old American model donated by a friend. As he told me in his 2009 email, their main business is metal buildings, outboards are a small sideline. The second outboard should be a four cyl. Boxer with 500 cc and 70-120 hp. The motors are direct injected like the Evinrude E-Tec. Arens was not aware that even the E-Tec 15 and 30 hp motors are direct injected. I asked what kind of oil he uses, he said any cheap oil and pointed to the shelf. He even tries 100:1 which is pretty extreme above 6000 RPM. The idea is to see if the motor can be damaged but he only had 70 hours of testing time on the powerhead. I told him about Evinrude XD-100 oil, made specifically for direct injection (it runs fine in our 1979 Johnson 75 at 6800 RPM, in our 1981 Evinrude 15 at 6500 RPM, and in our 1983 Johnson 35 at 6100 RPM, in all cases at 37:1). He was interested in that. The problem is to meet the E.U.'s too-strict emissions rules and the Evinrude does that, it’s the only 2-stroke outboard allowed to be imported new into the E.U. (there’s no rule against shipping an older 2-stroke to Europe).

Arens believes he can get 30 hp from 250cc (2 hp/c.i.) without the expansion chambers. His evidence so far is that moving the pipes has no effect. All the direct injected Evinrudes all have exhaust tuning, the 30 hp Evinrude has a rather long exhaust megaphone inside the exhaust housing. Almost all 2-stroke outboards since about 1970 have that, even the 1970s era 4 hp Evinrude weedless model has a tuner that boosted it from 3 to 4hp.

There were shelves and trays of parts. Arens showed us new cylinders and pistons made there, and the old rotax cylinders. We also saw ignition parts, all parts for the new motors should be made in Germany except the rods and bearings, those come from Japan. The rods are of one piece construction like the König. We also discussed gearcases and props.

We wished Holger Arens and his bold project well and headed north toward the Baltic in rain. We were very grateful for the time he spent with us!

Here's a link but the motor shown is an artist's drawing, the exhaust housing, gearcase and cowling don't yet exist


Clearly, the artist who drew the gearcase did not pay attention to hydrodynamic principles! A more complete description of our Arens visit will appear in The Antique Outboarder.

I'll add a note on German culture that Wayne Baldwin can verify from his time in Berlin in the 1970s. First names are never used until later after the older person suggests it to the younger one. Until then, it's Herr or Frau so and so. I was the older one and felt it was too early to suggest informality, especially as Arens is an accomplished engineer.
As Lars will likely verify, Scandinavia relaxed away from that formality sometime in the 20th century.

09-17-2011, 06:51 PM
If you scaled down your images to about 1,000 x 1,000 they will be much easier to view.

There is a group on Facebook of east block outboard racers that you may be interested in.

Mostly Czech, but some Polish, Russian and East German racers and cold war motors.


Master Oil Racing Team
09-17-2011, 07:09 PM
Very interesting Joe.

Smokin' Joe
09-17-2011, 07:10 PM
If you scaled down your images to about 1,000 x 1,000 they will be much easier to view.

There is a group on Facebook of east block outboard racers that you may be interested in.

Mostly Czech, but some Polish, Russian and East German racers and cold war motors.


I did that now, they're still too big. Maybe even smaller? Thanks, Sam!

01-04-2012, 07:01 AM
... with two carburetors ;)