I have a 1997 25hp, Mercury, 2 stroke that I purchases used and was in need of several items to make it whole. I now have the motor running and it runs very strong. The person who had it before me had the idle set very high and it seemed to be running very rich. I set the fuel ratio per the factory setting and it would stall when put into gear and when throttle was given. I screwed the the fuel mixture screw out one turn and the motor seems to run great. The motor does run rough at low RPM's but smooths out at little over 1/4 throttle. I have ran the motor two times now with mostly slow speed running. When the motor sits after use there is a very large puddle of dark black oil on the ground. I am used to seeing this but no where near this much. Question? Could dirty carb be to blame and I am running it too rich to compensate? Question? What fuel mixture are you running on same motor? I am running 50:1 but was wondering if anyone else uses different for this motor???? I am very happy with the power the motor is producing and as it is set right now it starts easy, and runs like bat out of hell. Just little rough at low speed before the power band.