"It works great and saves money on fuel," says Charley Marley, Nokomis, Ill., who converted his Case 830 65 hp tractor to run on propane.
A few years back, Marley started running a stationary Oliver 1650 tractor powering a corn dryer off the fumes from a 500-gal. propane tank -- the same tank that supplied gas to the corn dryer. The system required the use of a type "Z" gas controller made by Garretson Carburetor Systems, Roswell, New Mexico.
With gas prices rising rapidly, Marley recently decided to dig out the old gas controller and rig it up to burn propane from a much smaller, 30-gal. tank which he mounted on front of the tractor.
"With gas selling so much per gallon but propane for cheaper, it cuts my fuel bill in half," says Marley. "I think the same idea would work on any smaller tractor equipped with a carburetor. It won't work on bigger tractors, because the propane can't be vaporized fast enough to supply enough power. However, I don't use my tractor for real heavy work. I just run a small mower and baler, and the 30-gal. tank and controller can supply plenty of gas to handle those jobs."
He mounted the 30-gal. tank on a couple of steel rails that bolt to the sides of the tractor. To burn the gas, he simply drilled a 1/8-in. dia. hole into the bottom of the carburetor and ran a copper tube up into the venturi valve. Vacuum created by the venturi opens a diaphragm in the controller, pulling in gas.
A pressure valve on the controller shows how much vapor is entering the carburetor. Another valve can be adjusted with a screw to regulate the vapor flow rate. A shut-off valve on the hose at the propane tank is used to turn the system on or off.
Marley has noticed one other big difference when using propane. "The engine on an ordinary gas tractor coughs and belches, but once you convert an engine to run on propane it runs quiet, just like a fuel-injected car. And the engine oil stays clean. In fact, the longer the tractor runs on propane, the cleaner the oil seems to get," he notes.