Personal watercraft use is viewed by many people as one of the worst activities out there for the environment. And while the environmental issues that surround PWC are numerous, the one that has really mobilized the "green" movement is the fuel problem. It all comes down to the type of engine employed in many PWC.
Until recently, all personal watercraft ran on two-stroke engines. Two strokes are notoriously bad for the environment for several reasons. First, they don't just run on gasoline; they run on a mixture of gas and oil. Burning oil is even worse for the environment than burning gas, because it doesn't burn very well.
Second, traditional PWC two-stroke engines are so inefficient they end up dumping up to 30 percent of their fuel into the water unburned [source: BWN]. In a single hour of run time, a 2000-model PWC will dump about 4 gallons (15 liters) of unburned oil and gas into the water [source: CO Parks].
Historically, PWC two-strokes have had no pollution-control devices at all. Before new U.S. Environmental Protection Agency (EPA) regulations went into effect in 2006, which require the engines to comply with the Clean Air Act of 1990, they were not required to have catalytic converters to limit emissions or to institute direct-fuel-injection systems to try to cut back on the amount of unburned fuel they release [source: VLRS].
These fuel issues aren't so different from other watercraft two-strokes, but PWC draw special attention because they're so popular and because purchases have grown so quickly over the last couple of decades. PWC growth far outpaces other watercraft growth.
In the last 10 years, since the PWC-related outrage of the late 1990s, the industry has made engine changes. Many PWC now have cleaner four-stroke engines, and lots of the ones that still have two-strokes have been updated to have direct fuel injection, catalytic converters and other pollution-control measures. These cleaner PWC are allowed in many recreation areas that have banned the older, dirtier models.
But dozens of recreation areas, including most national parks, still have a ban in place. That's because the fuel dumping is only a part of the problem.