i think he would put way more into fixing that engine than it would be worth. Ive never pull auto parts out of a junk yard to fix an outboard, supposed it might be possible but there are just to many variables IMO to have something reliable when your done. But i can also see why you wouldnt want to spend the $3000 on a new powerhead from Honda for that engine.
i was just reading a trade magazine and there was an article on a company called MRS that seaid they had remanned Honda blocks. Dont have any experience with them and disnt have much info on their websitembut might be worth a phone call.