2000 sea ray runs rich. 5.7 mercruiser tbi

I have a boat in the shop I just can't figure out. It's a 2000 Sea Ray, 21' with a 5.7 Mercruiser MEFI 1 TBI.It runs rich always. Customer states it ran well when put into storage last year, has run rich always since being put into service this last session. Engine appears to be in good health...