93-95 Yamaha V6 crankshaft pitting problem

hello all,<br /><br />I have a 1993 Yamaha 175HP with low hours. It has always been carefully maintained and serviced. Recently we cooked a piston. Whilst phoning around for quotes on repair an outboard rebuilder predicted that, when the engine was dismantled, we would find pitting on the crankshaft. He was right! The pitting is on two journals only. My mechanic has refused to supply a warranty on the rebuild, if the current crankshaft goes back in the outboard. I took the crankshaft to a metallurgist for examination. He told me that the problem has been caused in the original casting. Without getting too technical, he says that spheroidal graphite accumulated in spots on the crank's surface. I am currently negotiating with Yamaha over a discount on a replacement part. If anyone has heard of a similar problem I would really appreciate a quick update from you.<br /><br />Thanks in advance<br />Andrew