oil pump problem on yanmar yse 12 ?

Hello Andy
I am not that familiar with the workings of the YSE although we have a 10hp in our boat which has been reliable as clockwork for five years.However,I would say you have a fault with what is called the "end float"of the crankshaft.If there are thrust bearings on the crankshaft and I am sure there would be they are probably out of tolerance allowing the crakshaft to float too far and score the items you describe.Try any Haynes or engine manual for "end float" to give a more detailed description.We had this on a VW Golf GTI once.It is quite rare these days.
Regards
Howard

Howard Hancock
October 2008