Since a 1999 ban on two-stroke, carburetor engines went into full effect in 2001, levels of burned and unburned gasoline products in Lake Tahoe have declined by 80-90 percent according to the Tahoe Regional Planning Agency (TRPA). The 1999 ban was instituted by the Governing Board of the TRPA, a bistate organization established to protect the lake. The board voted in favor of the engine ban after it reviewed data that estimated each day of the boating season resulted in carbureted two-stroke engines releasing 770 gallons of fuel into the lake.
Most of the people who use Lake Tahoe for drinking water live on the Nevada side of the basin. At one point prior to the ban, some residents tasted a turpentine-like flavor in their water. It turned out the gasoline additive MTBE had tainted their drinking water supply. MTBE has been banned many states and a federal ban on MTBE has been proposed.
Even with the ban, gasoline products still end up in the lake. A carbureted two-stroke dumps about 30 percent of its fuel into the water. Four-stroke and fuel-injected two strokes, which are the type of engines allowed on the lake, release between 1 and 2 percent.
The TRPA has a deal with boat engine manufacturer Evinrude, to use its latest fuel-injected, two-stroke engine. The agency is scheduled to receive Evinrude’s 2005 E-TEC engine, its most environmentally friendly and powerful model to date, this fall. According to Evinrude, the engine releases no unburned oil-gas into the water and burns all the oil put in the engine, which eliminates the need to recycle oil.