Diesel outboard

Yes it would be a good auxillary.

 

To perform well as an auxillary on a trawler it would need to have low gearing and swing a big prop, any idea of the reduction on this motor?

Steve.

 

Does neither from memory, ratio is about 2:1, and only max. 20" leg available in the size being discussed. Useless for a trawler.

 

My thoughts exactly, from what I can tell the only true high thrust outboard made is the Yamaha 9.9 with a 2.92 reduction, all the other brands are 2.31 with smaller props. Unfortunatly the 9.9 is a bit small for a trawler.

Steve.

 

I've often thought it would be possible to make your own diesel outboard.

Buy an old big 200hp outboard leg, some even came in extra long shaft lengths, and mate it up to a diesel saildrive engine with its 90 degree gearbox. This way you get a big prop and strong leg with the tilt mechanism.

I think the biggest saildrives are about 70hp which sounds perfect for pushing a big boat a hull speed; and you get the benefit of a Volvo or Yanmar engine and easy accesses to spares etc .

The engines could bet attracted to the OB leg with a simple steel frame as one unit, or driven with a shaft from the deck with UV joint.

Any one got any idea of the gear ratios to make this work?

 

Such thoughts have probably occurred to a few people, you have the issues of getting the right final gear ratio and propellor size right, and dropping a heavy engine on an outboard leg could create some serious balance problems ! But a big outboard leg should cope with the extra torque OK. The scarcity of diesel outboards shows little sign of changing.

 

Maybe a better plan would be to get a very big capacity petrol outboard, sleave the cylinders to bring it down to say 1600cc/1.6 ltr capacity, and convert it to diesel. Deck the block to get 16/1 compression; no problem with block strength.

A fuel injection pump off a small Vw diesel car would work perfectly, and from memory would produce about 70-80hp.

This way the OB engine block would already be in a vertical position, and all the lubrication pumps and holes would have already be designed to operate vertically. The balance of the OB would remain unchanged as well, the steering and tilt remains standard.

Standard spares would still fit.

........I seem to remember a large v8 American engine was successfully converted from petrol to diesel, and sold in large numbers. It was available in the UK as a conversion for the landrover.

any ideas what large OB would make a good candidate for the conversion?

 

Apologies to Hastings Harry for hijacking your thread.

I have started a new thread on this subject.

 

nirvana
diesel outboard that replaces a SI engine, still waiting

 

Hi Hastings Harry,

What happened with the diesel outboard tests? Considering buying one.

Cheers
Christian
Hong Kong

 

Having had time to cogitate on diesel outboards, I've come to this conclusion.

The Chinese normally reverse engineer western technology, making it cheaper because of the lower employment costs. The products that are manufactured under western supervision are very good; but the Runsun diesel OB is designed and manufactured in China.

A cynic would say how come the big OB manufacturers haven't brought out their own diesel models?

As we know it's very difficult to design a good engine even here in the west; the Chinese could have hit it lucky with this innovative design, but it's unlikely. Making a lightweight diesel OB is going to need exotic alloys, a highly specialised and expensive undertaking, and the Chinese are already know for the low quality of their castings on machinery.

The Yanmar diesel OB is the only mass produced model ever manufactured(there were a couple of others), and they stopped production because the price became so high it was unsaleable.

Maybe the Runsun is fantastic...who knows, and who is going to be brave enough to take the gamble?

 

Can the Chinese make a diesel that can pass any sort of emission test?
Without that there is no market as only the west could afford a diesel outboard

 

Afaik the Runsun hasn't passed any emission tests, which will severely limit it's market; but I suppose they will sell plenty in a China and the Far East where there are no tests.

I think Hastings Harry has had problems getting the engine to rev although it's quoted power is at high revs; but maybe it isn't designed to rev in real life!

 

G'day all!

Sorry for the silence, life has a habit of getting in the way of the best laid plans and boy I've been busy. We now have agents in NSW, Vic and Tassie as well as New Zealand. RUNSUN Australia is growing

My 40 Hp diesel outboard motor is gone, I sold it to an existing diesel outboard user and our new Sydney agent. Garry White. To see where it has gone please search "coffee boat Sydney".

It doesn't matter if diesel or petrol, 40 hp is 40 hp is 40 hp and you can muck around with props till the cows come home. It won't increase the horsepower.
My boat needs minimum 55 hp as per manufacturer specifications. So we will try the 60 Hp turbo Vee Twin.

I took my boat up to lake Eildon and goofed around on the lake over 3 days. Approximately 7 hours of use at pretty close to full throttle left my 23 litre tank just above 1/4 full. Because the boat is too big, it won't plane happily without sufficient power so most of this was at around 20 km/h. It sounds soooo good when you wind it out though.

It is interesting to read people's assumptions about the Chinese. I have watched the quality and the technology on these motors improve so much in the 18 months I've been dealing with RUNSUN. These people love to learn and improve. At present, their economy is 1/4 the size of the US. Predictions are that they will be bigger in around 15-20 years.

I have only 3 months ago sold my first couple of outboards because I had trouble selling what I received, but having seen the current range of motors, I'm selling nicely and the orders are coming in consistently and my customers are happy. See here for the new hood- http://www.dieseloutboardsvictoria.com/

Hope all is good in your world
Cheers Phil

 

>.I seem to remember a large v8 American engine was successfully converted from petrol to diesel, and sold in large numbers. It was available in the UK as a conversion for the landrover.<

This was after they scrapped the concept of using an existing V8 block, after thousands of diesel engine failures GM cast a special diesel block of superior alloy , with far better studs , forged crank and many other mods.