Boaters and fishermen who use Occoquan Reservoir are worried about a proposal to eliminate gasoline-powered engines from a large section of the impoundment.

The Fairfax County Water Authority has asked Prince William and Fairfax counties, which about the 16-mile-long reservoir, to pass local ordinances limiting the size of outboards and restricting their use to certain areas.

The proposal is to be aired at public hearings at 7 p.m. Tuesday at Garfield High School (Prince William) and at 2 p.m. June 30 in the Massey Building, 4100 Chain Bridge Road, Fairfax.

Currently, Fairfax County limits outboards to 10 horsepower or less in its portions of Occoquan, and Prince William has no limits. There are no areas on the lake from which outboards are excluded.

According to Fred Griffith of the Fairfax County Water Authority, the agency has proposed that an area from the Occoquan dam to a spot about 4 1/2 miles up the reservoir be closed to outboards.

The remaining 12 miles would remain open to outboards of 10 h.p. or less.

Fishermen and boaters are piqued by the proposal because they can't understand why closing such a section would affect the quality of water.

Griffith said the authority has no indication that outboard use is damaging water quality measurably, but added, "We know that emissions from combustion motors can be poisonous -- leads, hydrocarbons, heavy metals. . ."

"We don't have a problem now that we know of," he said, "but we're trying to get the mechanics for control so that we can control it if a problem does develop."

For example, he said, "We could have a tremendous increase in the number of people who use the reservoir. It could become a significant problem. And we'd have no practical vehicle for control."

All of this strikes some of the thousands of people who use the reservoir for fishing and boating as specious reasoning. A petition opposing the proposal is being circulated at Lynn's Store on the Occoquan River, and Harold Dutton of the Virginia Bass Fisherman's Association said his organization and others will be representing boaters and fishermen at the public hearings.

Said game warden John Berry of Prince William County, "They're talking about pollution and there's no evidence that a few outboards hurt anything.

Berry and others cited their fear that the water authority is seeking "a foot in the door," so it will have coantrol to close the reservoir to all fishing and boating in the future.

Griffith said that wasn't the aim, but conceded that the proposal does state, "The location of the markers (identifying the closed area) . . . shall be as established from time to time be resolution of the boards of supervisors as necessary for public health, safety and welfare."

"They could move it so that no boats could get in," he said.

Under the current proposal, the no-outboards line would cross the reservoir at a point about a half-mile below Fountainhead Marina, and powerboats would be excluded from any waters downstream of the line.

Griffith said the water authority is in no hurry, but hopes to have the proposal approved by the end of summer.