Got Propane? Run Your Outboard Motor on It

By Tom Tripp
Could This Be Your Next Dinghy Gas Tank?

Could This Be Your Next Dinghy Gas Tank?

Well, soon maybe.  In my apparently Quixotic quest for a single fuel for vessel, tender and toys, I keep looking for new ideas.  Using propane as fuel for an internal combustion engine is not new, but it is for a modest outboard application.  A company I can only identify so far as Marine Green (more on that later) has posted a video on YouTube that shows a small outboard running on what appears to be propane from a recognizable tank near the transom.

To quote the YouTube poster, “The ongoing progress of Marine Green’s R&D program. Propane is a better alternative fuel than other fuel sources. Safe, reliable, it does not go bad, and emits much fewer harmful emissions than gas… ”  Here’s the video:

 Is propane really a good fuel to use for your outboard?  Possibly.  We’ll have to wait and see Marine Green’s final performance and emissions numbers, but we do know a little bit about propane, generically, as a fuel.  Check out the table below to see how propane ranks in terms of its energy density.

Btu Content of Common Energy Units

  • 1 barrel (42 gallons) of crude oil = 5,800,000 Btu
  • 1 gallon of gasoline = 124,000 Btu (based on U.S. consumption, 2008)
  • 1 gallon of diesel fuel = 139,000 Btu
  • 1 gallon of heating oil = 139,000 Btu
  • 1 barrel of residual fuel oil = 6,287,000 Btu
  • 1 cubic foot of natural gas = 1,028 Btu (based on U.S. consumption, 2008)
  • 1 gallon of propane = 91,000 Btu
  • 1 short ton of coal = 19,988,000 Btu (based on U.S. consumption, 2008)
  • 1 kilowatthour of electricity = 3,412 Btu

Source:  U.S. Energy Information Administration

You can see that propane has about 26 percent less energy in a gallon than a gallon of gasoline, and nearly 35 percent less than a gallon of diesel.  That means that you’re not gonna get as far on a gallon, but if range isn’t an issue and if you’re already carrying and monitoring propane availability, it might be a solution.  It’s hard to tell what size outboard is in the video; but I might be anywhere from a 9.9hp to a 25hp unit, based just on appearance.  We’ll have to wait until the company’s website is up and running to get more details.  I have also reached out to an individual well-known in passagemaking circles to confirm a rumor that he is at the center of this project.  I’ll let you know what I hear from him.

Ultimately, I would still like to see someone like Evinrude take one of its multi-fuel E-TEC models and just certify it for diesel.  It will already run on the stuff, as well as practically everything else out there; from gas to Jet fuel.  Yes, I know diesel fuel is harder on an engine and it would require beefing up key components, but there are a LOT of diesel-powered yachts out there who would love not to have to carry gasoline for their tenders and dinghies.

Copyright © 2009 OceanLines LLC

Tom Tripp

Tom is the publisher of, a website about passagemaking boats and information. He is also a contributor to Chesapeake Bay Magazine who has been at sea aboard everything from a 17-foot homemade wooden fishing boat to a 1,000-foot-long, 96,000-ton, nuclear-powered aircraft carrier.

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