A Bigfoot outboard is an outboard engine designed for larger private watercraft such as houseboats or pontoons, made by Mercury Marine. "Bigfoot" is a trademark registered by Mercury and refers to a specially designed gear case.
Engines made by Mercury featuring the "Bigfoot" gear case are all four-stroke (the most common kind of engine, featuring intake, compression, power and exhaust). They are available in 40hp, 50hp and 60hp versions as well as a 9.9hp model.
Bigfoot Gear Case
The Bigfoot gear case is built longer with larger parts. This provides greater control and thrust, specifically designed for larger loads, according to Mercury, which also states that the larger parts make the engines more efficient and reliable.
A Bigfoot outboard is best suited for larger boats and boats whose design creates water turbulence around conventional engines. This is because the longer gear case pushes the prop down further into the water -- where it is not disturbed by turbulence from the boat -- and the larger gears provide greater thrust and control.