Adk1,
I matched up the numbers on the prop of my 95 Starcraft Islander 221v 4.3l and replaced it with a new mercury prop part number 48832830A45, BLKMX 14 1/2 R1 from local dealer. I've used it for past few years with no problems. I'm not sure if 1991 would be any different then 1995, but I found that the cost of reconditioning wasn't all that different from purchasing new especially if you have damage to more then one blade. good luck.
Jay