One look and you know Big Ed Lewis is not the kind of coal train you want to break down in front of. He goes 6 1/2 feet straight up and about 2 1/2 across.

Lewis knows the effects his massive bulk has on mere mortals and he tries his best to put us at east. Still, folks freeze.

"I had one guy last fall out here fishing for big smallmouth," Lewis announced from the ozone. "The fish were being contrary. We were trying everything. Finally he got one on, and I know that fish had to go four ponds.

"The guy was scared, you could see it, but he held on pretty good. He kept calm and let the fish run. He couldn't even budge the fish - couldn't gain an inch.

"Everything was going fine. He had his rod tip up and he was waiting it out. Then the fish turned and came straight for the boat going like 60.

"Well the guy just froze. He never even turned the crank on the reel and that fish went right by him, took a jump and spit the hook.

Now I try to stay calm, but I wanted that fish in the boat. I cussed him (The Angler) pretty hard before I caught myself. It was one of the few time I ever lost control."

There is not room on the Queen Mary for a fuming Ed Lewis and the object of his wrath, let alone on a 14-foot river boat. But Lewis cooled it, and next thing you know he had the client locked on a 3 1/2-pounder. It did not get off.

Heaven help us if it had.

Lewis is from the big country up around Hagerstown, where Maryland skinnies down into a little sliver that separates Pennsylvania and West Virginia. Here mountain streams fill the shallow, rock-strewn bed of the river that grows to a seaport by the time it thunders down to Alexandria.

This is the other Potomac, clear and fast running, dotted with fish weirs the Indians built hundreds of years ago.

Lewis has fished here all his life. He knows where the Indian fish traps are. He can visualize boulders where the river bellies down, gravel beds where the riffles dance. He can take his elegant johnboat through chutes that would give kayakers a fit.

During the week he holds down a job at the GE plant. On weekends he comes to life, leading city slickers to holes where muscular, sporty smallmouth lie. Big ones.

The smallmouth bass is to its heraled cousin, the largemouth as a bantam rooster is to a barnyard hen. Largemouth have it on size, but they can be lugubrious and lackluster in the fight. While smallmouth scrap like Sugar Ray Leonard, they tend to be small and the river fisherman can get tired of endless hooking 10-and-11 inch fish.

Lewis wants the best of both worlds. He loves the smallmouth's fire but he wants big ones. Over the years, he's worked out a technique that brings them.

He shares his tecnhique for the almost preposterous fee of $30 a day. "Be here at 5:30," he told me. "We want to catch the early feed."

Just after 6 we were on the river, putting in at the Hancock public boat ramp. With the bow still up on shote Lewis rang the school bell.

"Now I'm going to show you a few things. We're going to be fishing mostly plugs, and there's a lot of overhanging brush up here. You have to cast flat, like this."

He flung a Rebel diving lure out along the length of the boat ramp. He was still talking, cranking it in, when the line went taut.

"Hey, I got a fish." The line zigged across the ramp and in moments a 15-inch smallmouth was in the net.

"I hope that won't jinx us," said the big man.

It did.

As hard as we worked we couldn't find another fish that size as we moved eight miles upstream. Discouraged, we started drifting down. Lewis was lazily cranking a plug back at an outcropping called White Rock.It was practically to the boat when three black shapes appeared in the clear water. One of them bit and we had a keeper small mouth.

"Drop the anchor," I hissed. "Let's get 'em all."

We settled in at White Rock. Time lurched along like the endless freight trains on the mountainside track above us. We worked the rocks, worked the eddy, worked the fast water and the slow, but all we got were a few little fish.

I was pumping a plug back in the deep water when at last the heavens parted and my lunker made its bid. It plunged, leaped, dived, gave up, fought again and finally came to the boat, shaking and splashing.

We fondled it, admired it, laughed about it, measured it, weighed it (2 1/2 pounds) and then Big Ed looked me in the eye.

"What do you want to do with him?"

"I want to put him back."

"Good," said Ed. "In a couple of years he's going to be a fine fish."

At his pleasant rates, Ed Lewis is just about booked solid for charters this year. He may have a few dates, and if not he has a friend who occasionally takes charters. Both prefer to take only one fisherman. For two, the rates go up and there really isn't room to fish properly.

Write him at Rte. 1, Box 149D, Fairplay, Md., 21733.