PORTLAND – Tom Johnson of East Greenwich, R.I., has been a pro golfer for 14 years, but he was always in awe of the people he was playing with whenever he participated in a tournament.

“I’m a self-deprecator,” said the 40-year-old Johnson after Wednesday’s opening round of the 86th Maine Open Golf Championship at Riverside Municipal Golf Course.

Rich Parker of Lebanon, N.H., has been working to cure Johnson of that, telling him he’s as good as anybody he’s competing with.

“Parker convinced me that I can play, that I should have the confidence to believe in myself,” said Johnson, who showed what that confidence can do when he posted an 8-under-par 64 Wednesday for a two-stroke lead over the rest of the field of 138 golfers.

Johnson’s “lowest under-par round ever” late in the afternoon carried him past a talented group of golfers at 66 comprised of Jerry DiPhilippo of Gorham, John Hickson of Newry, David Bowyer of Southport, Conn., and Todd Westfall of Clendenin, W.Va.

Another stroke back were low amateur Ben Daughan of York, Biddeford native Casey Bourque of Lake Winnipesaukee (N.H.) Country Club, and, ironically, Parker.

Defending champion Kirk Hanefeld of Bolton, Mass., posted a 1-over-par 73.

Mark Plummer of Manchester and Shawn Warren of Windham were two strokes behind Daughan among the amateurs.

The field will be cut after today’s 18-hole round to the low 40 pros and ties and the low 22 amateurs and ties for Friday’s 18-hole finale.

Johnson is gratefully accepting the new-found confidence Parker has instilled in him, which Parker began doing during the Greater Portland Open in June.

“He told me that I should be doing better than I was, that I was a better player than I thought,” said Johnson.

Since then, Johnson has finished tied for third in the Greater Bangor Open three weeks ago and tied for second in a one-day event at Manchester, Conn.

Johnson said what he used to do during a round was get to a good score, such as the 6 under par he was after 13 holes Wednesday, and think, “If I bogey out from here, I still shoot 71.”

“[Rich] taught me to stop doing that,” said Johnson.

He parred the next two holes, then birdied 16 and 17 to get to 8 under. On 18, he left a 40-foot putt a few feet short, giving his “evil” thoughts another opening.

“I thought if I two-putt, I still shoot 65,” said Johnson. “Then I stepped away, [changed my thinking,] and made it.”

Johnson put a lot of the credit on his putting, too, which he admits isn’t the best part of his game. Wednesday he hit 14 greens in regulation and took only 24 putts.

“It’s amazing when you’re putting well how the game changes,” he said with a chuckle.

Confidence and putting haven’t been the only things he has had to overcome. He suffered kidney failure in 1998, but continued to play even as he underwent dialysis treatments.

“Dialysis was hell,” he said.

Johnson underwent a kidney transplant in September 1998, and he has had a different outlook since then.

He plays out of Blissful Meadows Golf Course in Uxbridge, Mass., and works as head of instruction at Golfers’ Warehouse in Cranston, R.I.

“Golf is important, but I’m not going to be a [PGA] Tour player. If I can compete with the New England guys like Hickson, that’s fine with me,” he said.

Except today, they have to find a way to compete with him.

Johnson, not usually a long hitter, was over the back of the green in two on the par-5 first hole (the normal 10th as the nines are reversed for the tournament), but he chipped on and made the putt for birdie. After sinking a 20-foot putt from the fringe to save par on No. 4, he added birdies on Nos. 5 and 8 to turn in at 33, setting up his 31 on the back.

DiPhilippo, the 1995 Maine Open champ, started his round inauspiciously with a bogey on the par-5 first hole.

“That’s not the start I wanted,” he said.

DiPhilippo began hitting good approach shots and putting well, he said, and he birdied three of the last four holes on the front for 33. Birdies on 10, 13, 15, and 16 more than negated a bogey on 11, and he posted another 33.

Hickson eagled the first hole, bogeyed the second, then birdied Nos. 8 and 9 for a 33. He birdied 10, 13, 15, and 17 on the back, surrounding a bogey on 14, for a second 33.