I have a 50HP Mercury 500 1970! WHOA, I know! Not very exciting, but would like to make it run. (Well it runs), but I don't like running it without water cooling the engine. Where do I begin!? I need the pump or impellor fixed?! Is that right!? I'd like to do this myself.. I guess I take off the bottom part of the motor, what do I look for, and do you think I need parts!? Any help is much appreciated! Thanks.