If National Park Service Director William J. Whalen has his way -- and it appears he will -- the days of the outboard motor in the scenic Grand Canyon are numbered.

The park service announced yesterday its intention to phase out the use of motors that propel thousands of raft-borne thrill-seekers down the tumbling Colorado River each year.

Whalen's decision to phase out the motors, during a five-year period starting in 1980, would apply to a 235-mile stretch of the river that lies within the boundaries of the Grand Canyon National Park.

Unless he hears a good reason that has not been raised before during months of hearings and testimony, Whalen said the decision will become final in a month.

Whalen's move has drawn oodles of flak, but he's sticking to his guns.

"I realize this is unpopular," he said yesterday, "but I feel that as the steward of America's park lands, i've got to call it as I see it. I'm an advocate of taking motors out of the river."

Whalen said he had "backed off" from banning motors from other rivers in the parks, but the Grand Canyon is where he's digging in and making his stand.

"The bottom line is that we are making a declaration of a value. This should be the epitome of a wilderness experience on a river in America. We want to make it a pure wilderness experience," he said.

A wilderness experience, ideally at least, would include as little noise as possible, so while the outboards will be bannect, oar-propelled rafting will be allowed to continue on the Colorado.

The plan to phase out motor use by 1985 on the rushing white water of the Colorado, one of the most attractive rafting stretches in the country, is contained in the environmental statement for the service's river management plan.

The statement and management plan were drawn up after studies, 13 public hearings and the review of more than 3,000 letters commenting on the proposals.

Whalen said that while motors would be banned, the park service is adjusting use-level schedules so that more visitors -- using oars, of course -- will be allowed into the park service-controlled stretched of the river.

"We have had a freeze on the number of trips motor and oar propelled, since 1972," he said. "I just don't buy the argument that the motor ban discriminates against people. I wouldn't be a party to that."

Motorized trips are conducted by 20 concessionaires licensed by the park service, who provide everything from life jackets to the raft to farewell dinner for the purchasers of trip packages. They carry about 12,000 passengers a year.

Concessionaries, understandably, are upset with the park service move to still their engines. (They can continue to provide the oar-propelled trips.)

"Our argument is that most people don't have time for the more time-consuming oar trips in the canyon," said Pam Manning of Arizona River Runners at Flagstaff.

"The park service is taking away the consumer's choice of propulsion. We just don't feel the motor really intrudes," she said.