Propane for the Dinghy Outboard Part 2

Marine Green Co-Founders Bill Parlatore and Howard Brooks test an early propane-powered outboard

Marine Green Co-Founders Bill Parlatore and Howard Brooks test an early propane-powered outboard

In a recent article here on OceanLines, we described a brand new development effort by a company called Marine Green to adapt smaller outboards for propane fuel.  Since that article, I have been able to talk with the co-founder of Marine Green, none other than Bill Parlatore, the founder and current Founding Editor-at-Large of Passagemaker Magazine. Bill described the work he and co-founder Howard Brooks have done so far, as well as what has yet to be done to bring the new technology to market.

According to Parlatore, the genesis of the propane-powered outboard was his bad experience with phase separation in an E-10 gas outboard. After having replaced the Fuel Control Module two times he began thinking about a different fuel solution.  Parlatore, not surprisingly, is a serious cruiser and his boat, Growler, has been featured on many pages of past Passagemaker issues. He knew that his outboard experiences were common in the cruising community, where the small outboards that typically power dinghies and tenders often go unused for long periods of time and are subject to the hazards of phase separation, not to mention the hassle of dealing with storing gasoline supplies for the motors. Parlatore says, “It’s the perfect example of necessity being the mother of invention.”

Parlatore sat down early last year with his neighbor, engineer Howard Brooks, and discussed creating a new fuel delivery system to power an outboard with propane. The key is the fuel delivery system, which replaces the carburetor or injectors and throttle body assembly on a gas-powered outboard.  Since much of the complexity of a conventional carburetor deals with the transformation of the liquid fuel into a combustible gas, the propane fuel module is much simpler — propane comes out of the tank as a gas.  That simplicity should translate into lower production costs down the road.

Although propane has a lower BTU content than gasoline per gallon, it has an equivalent octane rating of between 103 and 112, so the fuel economy difference is smaller than one might expect. Early testing suggests propane will deliver about five percent less performance over the entire RPM range compared to gasoline. Emissions, however, are expected to be substantially better and the company hopes to partner with a university engineering school to document the emissions performance and study manufacturing issues.

In tests over the summer, Parlatore discovered that the low-speed consumption was actually better for the propane, presumably because of the overly rich fuel-air mixtures common in gas engines at low RPM settings. Testing is focused right now on smaller engines that would be suitable for the dinghy/tender application, the center of which seems to be the 4-6 hp range. At 6 hp, says Parlatore, you’re looking at about a 55 pound engine, which most people can handle.  On the small engines, the propane tank is attached to the engine frame and is easily re-filled with a connector from a standard propane tank.  Larger engines have used typical 20 pound steel tanks, although Parlatore reports that a see-thru, 10-pound composite tank is not only much easier to handle, but is corrosion proof and allows you to judge remaining fuel levels accurately at a glance.

Summarizing his assessment of the propane potential, Parlatore notes that propane “doesn’t go bad; it doesn’t undergo phase change; it requires fewer oil changes for the motor, and gives you better economy and lower emissions.”  Applications to smaller outboards look fairly straight forward, although at higher horsepower levels the propane will need to be delivered as a liquid which poses more complicated engineering issues.  It’s clearly too soon to know how long before we will be able to buy propane-powered outboards, but you may be able to see them running at the upcoming Miami International Boat Show in mid-February.  Stay tuned.

Copyright © 2009 by OceanLines LLC

Posted by Tom in Construction & Technical, Cruising Under Power, Engines, Environment & Weather, Passagemaking News, People, Technology

Got Propane? Run Your Outboard Motor on It

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

Posted by Tom in Boats, Construction & Technical, Cruising Under Power, Engines, Powerboats, Technology