Problems With a 5 HP Thermoil Kerosene Engine

Paul B. Curtis shares memories of his family's problems with a 5 hp thermoil kerosene engine.

Vintage gas engines

A vintage tractor.


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A Gas Engine Magazine reader shares the difficulty his family had with a 5 hp thermoil kerosene engine. 

My earliest memory of a gas engine just about coincides with that of a steam engine (1913). To the best of my knowledge, we acquired our first gas engine, a used 2-1/2 hp Waterloo Boy sometime in 1912 or 1913 and it was in the family until 1943. It was used most of the time for pumping water and at times for running the washing machine. From the time of purchase, until sometime in 1916, it was the sole source of belt power on the farm. All this time it was used for sawing wood and grinding feed.

During this time dad decided to make it into a tractor so he wouldn't have to take the team whenever he went to do a job of wood sawing. For traction wheels he used the bull wheels from two old McCormick binders and drove them with the binder chains. There was no differential as such, but its function was performed by the ratchet sprockets of the binders being used as the final drive sprockets. Of course, due to this feature, there could be no reverse. The primary drive from the engine to the first reduction shaft was by flat belt from a clutch pulley on the engine. The tractor proved unsatisfactory, mainly because of lack of power.

In 1916 we purchased a 5 hp Thermoil Kerosene engine from Sears Roebuck, price $105.00. Now, this engine was actually a full diesel although it ran on kerosene. The fuel supply was contained in a 1-1/2 gallon tank mounted above and slightly ahead of the water hopper. Lubrication was by drip oiler and compression hard oilers. The engine could be worked hard all day (8-10 hours) on three gallons or less of fuel, but it took about a quart of oil.

The weakness of the engine was in the design in that it was merely a dieselized Economy or Hercules gas engine. The engine base, crankshaft, connecting rod and piston pin being interchangeable; except, there possibly being no opening for the igniter, the cylinders were the same. The trouble we had was that after the engine was somewhat worn, that on or in starting it would break off two of the six cap screws holding the cylinder to the base and strip two, thus leaving only two screws holding. This was overcome by having four one inch rods threaded on each end and four plates drilled to take the rods and using them for clamps over the water hopper and under the base.

In the winter of 1917 or 18 Sears called all these engines back in and shipped New Economy gas engines. They were the same size and they refunded the difference in cost. In our case, it was $30.00. That particular series of Thermoil engines was made in 5, 7,9 and 12 hp.