If its a 1995 it wont be an Opti so assume its a 2 stroke carb and yes it will be fairly thirsty. (9 gph plus at flat out). I think the boat will be a Deepsea 21 which is actually around 6.3m. They are very beamy, stable RIBs with a good ride for a baot of their size. However, build quality of BWM's was shall we say, a little variable, over the number of iterations of the company.
Check carefully for structural damage - major cracks and whether the deck still has its integrity. You may find that consoles, seats, grab rails etc may show cracking around them. (I had a BWM DS21 1998 where the hull was solid as a rock but everything fixed to it fell apart one way or another.)