I bought a 1987 Yamaha saltwater 9.9 electric start 20 inch 4 stroke in pretty good all original condition for a hundred bucks. I went through the carb, which was a little nasty, but now seems to be all good and clean. 2 problems: (1) to start this motor, I must put thumb over the air intake of carb. She dies when try to get to idle under 1800 RPM (idle jet adjustment seems to have no effect). The plunger at the top of the carb is automatically coming all the way down when it is running (should this happen?). Gas is dripping out of the throat of the carb. The float was working as designed to stop and start fuel flow. Above 1800 RPM she does stay running and pumps water well but runs rough. (2) Lower unit does function fine, however she is taking on a little water. Where should I start with this problem? Is it possibly a simple to replace seal at the prop shaft end? I?m new to Yamaha?s; I know these type leaks can be several things but was just wondering if a seasoned person could tell me what?s most likely. In advance, thanks for listening?Scott