Is Diesel or Gasoline Better for Workboats?

USCG New Response Boat Small is Highly Manuverable
A United States Coast Guard Response Boat Small Participates in an Exercise Off the Coast of Washington State. USCG

 

Big ships like the Maersk Triple E burn marine fuels that are heavier than regular diesel. These ships turn heavy fuel oil into forward motion with greater efficiency than any type of cargo transport in the past.

There are only a couple thousand very big ships in the merchant marine fleet. There are hundreds of thousands of smaller commercial vessels around the world. The collective impact of these smaller vessels is as important to the global fuel supply line as the fuel for larger cargo ships.

The smallest commercial craft use both gasoline and diesel as possible fuel sources. There is a contentious debate between the supporters of gasoline and diesel power. The philosophy and equipment is as variable as opinions on the subject.

Here are some pros and cons of each fuel.                                                                                        

Diesel Pros

  • Low sulfur production is now widespread and required in some areas for all diesel applications. In areas of full adoption, particulate and potent diesel exhaust fumes are noticeably reduced.
  • Less explosive potential is one of the biggest arguments for diesel because it doesn’t evaporate quickly and cause explosive conditions in the bilge.
  • Handling diesel is safer for workers who fuel boats. Sparks from dropped tools or static electricity won’t ignite gasoline spilled at the pump or from a can.
  • Diesel has more energy per unit of volume, or energy density, so range can be extended using the same volume of fuel.   

    Diesel Cons

    • Equipment is unavailable or expensive for some applications. No direct comparison is possible except in specific A/B types of testing because of the many variables involved. A rule of thumb is that diesel equipment costs around twenty percent more to purchase because of higher pressures and building tolerances. A compression ignition engine will often have a very long period of operation between service intervals compared to gasoline powered engines.
    •  Cold weather operations are difficult without proper precautions. Cold weather vessels are equipped with extra starting power and auxiliary heaters. Loss of main power in these conditions often means loss of the vessel to freeze cracking and eventual sinking. Still, any icebreaker that is not powered by a nuclear reactor is powered by diesel or diesel-electric propulsion. The real danger is for seasonal vessels to be caught at the dock late in the year and need a half day of preheating to start the engines.

    Gasoline Pros

    • The only choice for some applications like outboard motors which power many small boats in the commercial and military fleets. High efficiency outboards exceed the performance of a similarly sized diesel engine.
    • Less expensive than diesel and with fewer geographic restrictions on its use. Standard marine gasoline engines are allowed in any jurisdiction that allows combustion powered craft in its waters.
    • Widely available in small quantities. Trailered workboats can sometimes take advantage of fuel sources away from the dock. Diesel powered vessels on trailers can take advantage of this source but not every station has the correct color of diesel for marine use.
    • Lower cost of power plants since engines will see less internal strain they can be built with lightweight components.
    • Fast evaporation means small gasoline spills rarely endanger the environment.

    Gasoline Cons

    • Explosive fumes that form easily in many conditions require blowers and vents to be operated throughout the fueling process.
    • Leaking fuel is an explosive danger and requires the installation of explosive gas detectors.
    • Hazardous to handle and dispense
    • Increased insurance costs for gasoline powered vessels
    • Gasoline treated with alcohol such as ethanol will absorb moisture into the ethanol very quickly in some blends. Generally, most marine gasoline is free of alcohols to reduce moisture absorption in the maritime environment.