I just got my hands on an 8hp Mariner that I think is pre-1980. It is mint, but has been sitting for several years. I want to change the water pump impeller (which has probably taken a set)before I take it out. The serial number on the transom clamp bracket is 677 S 012037. This Mariner/Yamaha/Mercury history is a confusing mess! I hope one of you guys can help me out.