View Full Version : Semi-diesels

09-14-2007, 07:44 AM
In reading Maurice Griffiths 'The Magic of the Swatchways' he referred to boats powered by semi-diesels.

What are semi-diesels?

Paul Pless
09-14-2007, 08:24 AM
Its basically a diesel engine, except that there's a chamber in the the fuel injection system where the fuel is preheated and vaporized before being sprayed into the combustion chamber at the top of the compression stroke. Early variants even used open flame type torches to preheat the chamber, later models used electrical accessories.

Gary E
09-14-2007, 08:26 AM
My guess is that his "semi" actualy refers to Semi Tractor / Trailer... since all "semi" trucks are Diesel engine powered.

The Diesel Engines used in boats are the same basic engines used in trucks, but modified for marine use. The major engines in use today are from Cat, Cummins, Detroit, and the German MTU.

09-14-2007, 08:48 AM
My guess is that his "semi" actualy refers to Semi Tractor / Trailer... since all "semi" trucks are Diesel engine powered.when Maurice Griffiths 'The Magic of the Swatchways' referred to boats powered by semi-diesels he was in the +/-1930's I dont think that the Semi Tractor / Trailer were in general use then :confused:.

Paul Pless
09-14-2007, 08:51 AM
here's one running, love the way they sound: http://www.youtube.com/watch?v=qzx-yNgAV7o&mode=related&search=

Paul Pless
09-14-2007, 08:58 AM
here's another cool one in a boat no less;) : http://www.youtube.com/watch?v=fG3DhZf6nIc&mode=related&search=

Incidentally most of the old marine diesels are two strokes.

Paul Pless
09-14-2007, 09:02 AM
Ah I knew I'd find it, here's the one you really want to see: http://www.youtube.com/watch?v=vuNxFDkTp6w&mode=related&search=

09-14-2007, 09:14 AM
Given the time and location they may be talking about a hybrid engine found on British farm tractors that start on gasoline and run on heating oil when warmed up. Fergies were famous for them. it was called TVO (Tractor variation oil)

P.I. Stazzer-Newt
09-14-2007, 09:24 AM
Designating an internal-combustion engine of a type resembling the Diesel engine in using as fuel heavy oil which is injected in a spray just before the end of the compression stroke and is fired without electrical ignition. The fuel is sprayed into an iron box (called a hot bulb or hot pot) opening into the combustion chamber, and heated for ignition by a blast-lamp until the engine is running, when it is, ordinarily, kept red hot by the heat of combustion.

AKA Hot-Bulb.

The TVO thing is (was) essentially a petrol (gasoline) engine with a carb heating system to allow it to run on kerosene (paraffin) - you had to start these things on petrol, then once up to temperature, switch over to TVO (paraffin/kero).

The whole raison d'etre for the TVO thing was the Brit fuel taxation scheme - TVO allowed farms to use cheap (Low Tax) fuel without any risk of people running their cars on it - agriculture switched to Diesel (derv) and TVO was withdrawn from the market in 1972 or 3...

The last one I saw was in 1968 a Fordson Major, up a large hill in the south of Scotland attempting to do duty as a ski-tow in a place that only very occasionally had snow - probably the perfect example of a half-baked idea.

There you go, isn't the internet wonderful - yesterday you didn't know, tomorrow you won't care, but just for today you are slightly better informed.