From Correspondent Don Knapp

SAN FRANCISCO (CNN) -- California's polluted skies have promoted some of the nation's toughest automobile smog regulations, but there have been no such restrictions on the state's half million small boats and Jet Skis.

Many of the personal watercraft use a conventional two-stroke engine that creates as much pollution in two hours of use as a new automobile driven more than 100,000 miles, according to the California Air Resources Board.

A proposal before the board would block sales of such engines by 2001.

"The amount of pollution coming from these engines is simply staggering," said Russell Long of the Bluewater Network, a project of San Francisco's Earth Island Institute.

"Nobody even knew this until the (U.S. Environmental Protection Agency) recently took a look at them and they found out that ... these are one of the largest sources of toxic water pollution in the United States."

The simple design of the engine allows some of the fuel drawn into cylinders to pass through unburned into the exhaust system. That causes both water and air pollution.

"In a lot of these, you get 20 to 30 percent of raw unburned gasoline and oil coming directly out of the tail pipe, and these are the types of emissions that contribute to what people refer to as smog," said Richard Varemchik of the Air Resources Board.

There are new two-stroke engines that eliminate the problem, making it impossible for raw fuel to enter the exhaust system and go out into the water.

But the marine industry says it can't convert all of its engines by 2001.

The industry says it can produce cleaner marine engines by the year 2006, which falls in line with EPA requirements. But Air Resources staffers say Californians can't wait that long for cleaner air.