Jimmy Buffett, who opened a two-night stand at the Merriweather Post Pavillion last night, is going to have to work a little harder to outlast the critical acclaim accorded his early work. In the last three years, ever since the enormous success of Margaritaville," he's had a tendency to sail the same obvious waters, coasting on familiar musical currents.

Like the promising fiction writer who's found security gearing his work for the pulps, Buffett has dulled the edged that made his bench bums, paperless ship captains, smugglers, stranded tourists and seaward refugees vital and believable characters brought to life with caustic lyricism and wit. When Buffett moved from the edge of "A1A" to his 48-foot clipper, he distanced himself from the immediacy of his struggling vision.

Last night's performance concentrated on Buffett's uptempo successes, including "Magaritaville," "Cheeseburger in Paradise," and an old audience favorite,"God's Own Drunk" (courtesy of Lord Buckley). New songs like "Growing Older But Not Up" and "I Don't Know (What I'm Gonna Do When the Volcano Blows)" were predictably good-natured and just as typically unadventurous. Hs ballads, or more properly, laments, were far less effective since Buffett did them as solo as he dared. As Buffett the songwriter has weakened, Buffett the performer has been bolstered by the ever-larger Coral Reefer Band. They brought a finessed funkiness to Buffett's tropical but increasingly less topical langor. fBuffett should tuff it.