Popular Mechanics had an article on two cycle outboard motors.
These are some of the BSFC numbers for supposedly 115 HP motors.

Pounds of fuel burned is based on six pounds per gallon.

Brake Specific Fuel Consumption is in pounds of fuel
burned per hour per HP. This is for wide open throttle
at the top speed of the boat and just about max HP.

DFI is Direct Fuel Injection into the combustion chamber.
The Fisch system is used by Evinrude and Mercury, I think,
uses the Aussie ORBITAL air assisted high pressure injection
system more or less.

EFI stand for Electronic Fuel Injection and more or less
exactly the same as your car. The Honda is an adaptation
of their car engine.

                      GPH  Pounds  BSFC
Evinrude 2 cyc DFI    11.0  66.0   0.57
Honda 4 Cycle EFI      9.0  54.0   0.47
Mercury 2 cyc DFI     11.0  66.0   0.57
Suzuki 2 cyc EFI      16.0  96.0   0.83
Yamaha 4 cycle EFI     9.0  54.0   0.47     

The Mercury was significantly faster at wide open throttle so
I suspect the HP was higher and the BSFC was lower.

I cannot calculate the BSFC at 3500 RPM for these engines as I know
not the HP they were generating.

Big improvement in two cycle engine fuel consumption with high
pressure direct injection. Hopefully this will filter down to
the aircraft versions soon. Almost as good as a rotary :-)

Paul Lamar
 
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