Just picked up a 1970 Johnson 1.5 hp at a garage sale for $25, before trying to start, I removed the carb, and the gas tank, cleaned both out, put new gas (50-1) in the tank, filled up a garbage can with water, 14 pulls later it started, runs a bit rough at times, but fine at others, have tried adjusting the high/low, but think it might be the plug wire, as its taped in a few places and is so loose the end keeps falling out from below flywheel, does that sound like a cause of running rough? any other ideas? Impeller works fine, but noticed black oil in the water, any ideas? I'm not that mechanically inclined, can fix most, just can't diagnose. Thanks for any help