Golf is probably some kind of a mental disorder like gambling or women or politics."" That's the considered opinion of Kenny Lee Puckett, a thrice-married, 34-year-old touring golf pro who's spiritually akin to -- as well as the cussin' cousin of -- his Semi-Tough gridiron nephew Billy Clyde Puckett. Kenny is playing under the strain of a two-wife handicap -- Janie Ruth Rimmer, bosomy and ""dumb"" is leaving him for his best friend and golf rival; while his second -- liberal intellectual Beverly Tidwell -- is in a hospital bed trying to lick the Big C. Those who remember the simpler, rowdy high spirits and humor of its predecessor may feel Kenny Lee's anxious involvement with Beverly belongs on another fairway. Nonetheless he withstands a final round charge by Jack Nicklaus to win the National Open (thereby becoming the greatest thing to happen to Fort Worth since Ben Hogan and Byron Nelson). The semi-sensitive Puckett story -- all the way from his origins on his hometown Goat Hills course to his major championship win at Heavenly Pines -- revolves around not only his marital difficulties but also his good-natured cronies like Grover Scorner and mean critters evoked from his Texan boyhood days and particularly his first wife's hellbent brother Waylon. Lively off the rinks but as the nothing-is-dead-solid-perfect title suggests, Puckett's Dunlop 4, accustomed to the rough, lands just off the green. Still the gallery will be large.