New Diesel Outboard

THAT is very cool, it weighs about 100lbs more than the comparable 200hp Yamaha but the added torque and that 220amp alternator.... nice.

I really like the safety bonus of not having to carry gasoline onboard for the tender. I wonder what the sound levels are like compared to a similar HP 4-stroke gasoline outboard.

Probably the usual diesel chatter at Idle.
Having spent quite a few years of my life with Diesel engines, I like
It. (Looking for a diesel station wagon now, not many choices in the U.S.)
Is the pricing out yet on the OXE Diesel outboards?
The weight may be a problem if 100 lbs more that a 4-stroke gas engine

I am most probably the biggest fan of diesel outboard engines on this forum. And this for commercial shipping and for private boating!

But......

There are NO really usable diesel outboards on the market jet. The old Yanmar 35 HP diesel outboard was a very reliable engine with low fuel consumption but heavy and vibrating like hell. But with todays diesel technology, like injection systems (high pressure common rail) and noise / vibration lowering measurements, it would still be a good outboard engine. The only problem would be the high purchase costs. Far to expensive for a mass production leisure boatintg product. The one we had on my fathers yawl was sunk by my brother including the gig he was bolted on .

The German app. 70 HP turbo diesel outboard engine (Neander Shark) is far to heavy (155 kg) for private use and even more expensive. I am trying to buy a descent number of those engines from them (for our SOLAS RESCUE BOATS) for several years now but there is no evidence of any type of production jet.



These Chinese diesel outboards, which are sold through an Australian company in Europe are of lousy quality and performance, very noisy, unreliable and do not have any type of dealer or service network in Europe or in the US. We have tested two of them. The result of our specialists was there request to sink them in the deep open sea .

This new swedish diesel outboard engine is a new and totally different approach. Using a GM production 2 litre car engine, mount it horizontally and transmit the power via belt drives to the prop is an interesting idea. Modern normal and toothed belts can transmit pretty high amounts of power but their lifetime is rather limited.

I have two pretty big 24 Volt DC alternators each on my Volvo Penta D4-180 engines in my 50 ft inland waterway displacement boat. They work flawless for one season, may be for one an a half but around the belt drives in front of the engines, there is always a lot of black abrasion material located. Means, high torque transmission causes abrasion on belts. Plus those belts get pretty warm and that causes embrittlement.

The other and biggest problem on belt drives are constant and propper belt tension and belt oscillations especially on longer belts. On my powered glider with its 50 HP Wankel engine and its very long belt drive, it needs a lot of attention.



And this is the biggest problem I personally foresee with this new diesel outboard engine. Very high torque transmission via a pretty long belt and even with automatic belt tension, the regular change of this belt looks complicated and costly. And this Korean built GM diesel engine is not the optimum choice in my opinion. But on the other hand, this is the biggest advantage of this concept, the flexibility in using different types of available car diesel engines. Not only different ones, also smaller once are possible.

If they are able to get this belt drive long lasting and reliable and they are able to find a good production company with a good service network (like Volvo Penta or Mercruiser), it might be an engine to concider.

The back side of using production car diesel engines for boating or even for light aircrafts, is their availability over the years. Car companies change their engines with every new model and the OEM user of this engines might find itself without an engine for his product in the next year.

The Thielert Centurion Diesel engine (now Continental, which is based on a Mercedes car engine) for the Cessna 172, the Piper Archer and some UAV like the Predator, is a typical example. The small German company could not keep up with the pemanent engine changes by Mercedes, as each engine change caused expensive certification changes for the aircraft.



In my opinion, a turbo diesel Wankel engine or a OPOC double piston two stroke turbo diesel would be the optimum outboard diesel engine for leisure boating. Light, small, powerfull and both could be mounted vertically for a less problematic shaft drive.



Just my 2 (Euro) Cents

Because of its combustion process and higher bearing pressures, a diesel engine needs a more more solid design and will therefore always be havier than a petrol engine. But comparing this new belt driven diesel outboard with an equivalent petrol outboard, we have to compare two outboards of equal torque not HP, as torque means thrust. If comparing the 370 NM of torque of the Oxe diesel outboard with a typical petrol outboard from Honda, Yamaha or others of similar torque, you have to compare the Oxe diesel with an 250 to 300 HP petrol outboard. And those V6 or V8 heavy metals are in the 260 to 300+ kg range also. So not very much weight penalty, if at all.

But the difference here is the transmission. When dealing with large offsets between the crankshaft and the final power take off shaft (like on a sterndrive or outboard), you have only a few choices.

- a multi wheel spur gear (very heavy, relatively large and expensive and with a loss of efficiency of up to 5 %, depending of the number of wheels).

- vertical shaft (a normal petrol outboard has an engine with vertical camshaft and only one angular gear box. An engine with horizontal crankshaft would have two angular gearboxes, of which one has to do the reverse / forward and neutral shifting, effiency down by about 2 to 3 %)

- hydraulic power transmission (a very elegant way, mostly used for thrusters. Losses here up to 10 - 13 % and very noisy)

- electrical (that would place the electric motor into the water and would still have water cooling for the generator. Effiency losses even higher and up to 15 %)

- Belt or chain drive ( mechanically the most easiest way, with the toothed belts the efficiency is pretty high but the belt tensioner and belt oscillations will cost some efficiency. Modern materials like Kevlar, Carbon and Aramid or a combination of metal chain joints and carbon parts are making pretty reliable belt or chain drives).

Below the mechanical principle of a simple outboard engine as known by most of us.



One angular gear on the prop shaft which also does the shifting.

The the solution is very clear and easy. Horizontal engine with belt or chain drive (if long lasting and reliable) or a light and small vertical diesel engine with shaft drive.

Also knowing that an efficient turbo diesel Wankel engine is quite difficult to design (I believe John Deere had a turbo diesel Wankel engine ready for production), I am still thrilled by this type of engine.


This normal aspirated 50 HP engine is so small and low weight, that I am able to unsrew the whole propulsion system from my Glider in less than 5 minutes and carry it away with one hand (including beltdrive and propeller tower). Even if the weight of the engine would double with the diesel principle, it would still be a very small and light outboard motor.

But if somebody would give me the appropriate battery, I would only use one of those electrical outboard engines in the future . SF I Know.


Will say, the Oxe diesel outboard engine depends crucially upon the performance and reliability of the belt drive system.

Just my 2 (Euro) Cents

A little amendment to my statements about the Neander Shark Turbo Diesel Outboard. That monster is havier now, 175 kg instead of the proposed 155 kg and only 50 HP instead of 70 to 75 HP. And still no production but a lot of PR. To me it looks like, they want to sell the project to a stupid strategic investor or production company. One more high tech development for the Museum of technical astray ????????

OPOC means opposite piston, opposite cylinders and is the newer development of the old German pre WW II Junkers aircraft double piston diesel engine (Junkers Ju 86 and Stuka). The OPOC version, which has only one crankshaft, was developed by Volkswagen and as far as I know, is in a stage of protype testbed runs. And it is developed in a petrol and in a diesel version. Pretty complicated thermodynamics from what I have been told.

Found this about the present state of delopement of this OPOC diesel engine. The project moved to the US. Looks like it is hitting the market with these investors behind.

www.ecomotors.com




Smaller and bigger versions are under developement. Looks like a nice engine for light aircraft. May be the 2-stroke engine is back and alive.