Yanmar Dtorque 111 - world's first viable diesel outboard ?

Interesting Double con-rod arrangement

Claims -

"The Yanmar Dtorque 111 is lighter and more compact than petrol engines of similar capacity, has double the engine life, is much smoother, offers much better fuel consumption and running costs, produces significantly less toxic emissions, and with more torque much lower in the rev range, will thrust a boat onto the plane much quicker ... and that's before you consider the safety and ready availability of diesel fuel."

Game-changing Yanmar 50 hp turbo diesel outboard motor begins production http://newatlas.com/yanmar-dtorque-111-turbo-diesel-50hp-outboard/51675/

 

"The Yanmar Dtorque 111 is lighter and more compact than petrol engines of similar capacity" That claim seem rather dubious to me, 175 kg is a lot for 50hp. A Mercury 115 4-stroke weighs 165kg.

 

It may be a lot of things except light. Two cranks, steel girdle and liners, twice the number of rods and pins is a lot of heavy metal.

 

More interesting info here at the company site:
Dtorque | TURBO DIESEL https://www.neander-dtorque.com/
The two rods might reduce piston/cylinder friction during the power stroke. A square four with geared crankshafts (like the old Ariel motorbike) would also have perfect primary balance as well as 180 deg. firing interval instead of 360 deg.

 

"With maximum torque produced at 2500rpm, the 50 HP Dtorque 111 has more torque than the best-performing 70hp 16-valve electronic fuel-injected four-stroke petrol outboard on the market today. ... also use 35 per cent less fuel than petrol "

https://www.boatsales.com.au/editor...dtorque-111-turbo-diesel-50hp-outboard-59330/

No prices or availability from my local Yanmar dealer, so it looks like a year or two before I would seriously consider them.

 

I'm not sure torque is of much interest to most boaters, and this engine is way too heavy to be considered a replacement for engines of comparable output, for recreational use. Outboards are weight sensitive, and the trend in 4 strokes is to get the weight down further, even by dropping a camshaft to do so.

 

The fuel consumption shown in rwatson's original link, for the 90hp 2-stroke, seems way too high to me, instead of 32 l/hr at 4000 rpm, I would expect around 10 l/hr less than that, at least.

 

Depends a lot on usage

".... With the Yamaha F90 fitted to a 5.35m Bar Crusher we saw a top speed of 61km/h (33 knots) at 5700rpm with a fuel burn of 35.85 litres per hour while a more modest cruising speed of 33 km/h (18 knots) at 3500rpm delivered 10.85L/ hour offering a decent range from a 100-litre tank."

Yamaha F90 Four-Stroke Outboard Review - BoatAdvice http://www.boatadvice.com.au/yamaha-f90-four-stroke-outboard-review/