As such, the BGM system for gasoline provides a boater with three modes of operation: Gasoline-only, CNG-Only, and Advanced Hybrid. The Gasoline mode is the traditional mode of operation; CNG is the Natural Gas mode where only Compressed Natural Gas is used to power the engine; Advanced Hybrid is a dual- fuel mode that mixes Natural Gas with Gasoline at a variable rate, but it is primarily Natural Gas with a small amount of gasoline.
The following chart shows the Fuel Efficiency of a 21-foot long Chris Craft Scorpion 215 offshore fishing boat equipped with a single Yamaha Outboard F250 3.3L engine (250 Horse Power) and the second generation BGM Advanced Hybrid CNG System (right):
The fuel efficiency is displayed for each one of the modes of operation and the most efficient point highlighted with the display of its maximum efficiency. As expected, all three modes of operation reach maximum efficacy between speed and fuel consumption at a speed of 28 miles per hour. The interesting fact is the gasoline’s maximum efficacy is 3.3 miles for every gallon burned, but if the boat is run at the same speed under the CNG mode, the efficiency gets much higher to 4.9 miles for every gallon equivalent of compressed natural gas. This represents an increase of efficiency of 48% which means you are spending a lot less fuel to go at the same speed. The efficiency of the Advanced Hybrid mode is 4.3 miles per gallon, which is better than gasoline but not as good as pure CNG. This is expected since it uses primarily natural gas, but it starts using more gasoline after beyond cruise speeds.
CNG mode gives you maximum efficiency and maximum economy but it is a couple seconds slower to the boat on plane. This is primarily used by ferries, towing, salvage and fishing boats. The Advanced Hybrid gives you good efficiency and the same acceleration as pure gasoline,
30 | The Report • June 2017 • Issue 80
so it is a compromise between the best of both worlds and it is a favorite of first responders and patrol boats that require quick reaction time but can still take advantage of CNG.
The operator can switch between any of the three modes of operation at any speed and the engines can be started on any mode as well. This is a feature that gives boats great safety on the water, because if there is a problem with the gasoline
system, the operator can switch to CNG mode, start the engine and continue to operate (or return home). This is possible because the BGM add-on system is completely independent from the gasoline system and does not share any components with it.
On the next chart you will find the fuel consumption comparison of running the same boat in each one of the three modes of operation.
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