Convert Your Lawn Mower or Small Engine to Propane!

Reader Contribution by Derek Sherwood
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My fascination with propane as a fuel for internal combustion engines began in college, with a job at a local hardware store.  We had an old Caterpillar forklift that ran on propane.  I don’t know much about that lift – it was as old as the hills – but it had begun life as a gasoline-powered model.  You could tell because they had painted over the gas gauge when they did the conversion.  I remembered noting that there were very few mechanical problems with that lift in the eight years I worked there, and also that the exhaust had a mild, throaty burble and a barbecue-grill smell when you ran it.  I was teaching myself small engine repair as a side project and I remember thinking how it might be interesting to convert a lawnmower to run on propane.

Fast-forward about twelve years.  Having successfully worked on hundreds of small engines as a side business to help pay off my student loans, as well as learned how to work on cars and other mechanical equipment, I had forgotten all about that forklift for a very long time.  One night I walked into Sears and saw something on their clearance rack in the lawn equipment section that I had never seen before – A propane-powered four-stroke weedeater.  I didn’t really have the money for it, and I had a perfectly good gasoline-powered four-stroke weedeater at home, but I talked about it enough that my fiancée went back and purchased it for me.

The Sears weedeater was made by a company called Lehr Propane, and as I researched them, I saw that they also make lawnmowers.  I didn’t have the money for a $300 brand-new propane-powered mower, but I wondered if perhaps my old idea about converting a gasoline mower to propane had gotten any more feasible.  I decided to do a little research on the internet.  I found plenty of sites talking about how it could be done; however, none of them got into detail, and none of them really seemed complete.  There was a lot of jury-rigging evident, and a lot of bad advice.  I decided to see if I could make a set of propane-powered lawnmower plans that would allow anyone to be able to do it themselves – safely and inexpensively – and make sure it was done right, the first time.

The next few blog entries will be the results of this effort.  I spent many hours reading on the internet, testing different methods shown there, tinkering and modifying the design you’ll see here to come up with an inexpensive, safe way to convert a float-bowl carburetor, gasoline-powered lawnmower to propane with simple hand tools for around $120.  The conversion takes about 1-2 hours (depending on your skill level and whether you have all of the parts available before you begin), and when you are finished you will have a lawnmower which operates exactly as your gasoline mower did before, on 1-lb cylinders of propane which are easily refillable from a 25-lb grill tank.  We’ll talk about why you would want a propane-powered mower; the benefits of propane; the precautions for working with propane; and ultimately an overview of how you can complete the project.  I hope as well that you’ll consider purchasing the plans that I have made, which comprise over 17 pages and dozens of pictures that will cover step-by-step how to do this conversion with complete material lists and vendor contact information.  I sell them on Ebay for $5 per set, or you can contact me directly,

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