I bought a fleet of 9 used 2005-06 9.9 Mercury Four Stroke Motors from a local marina that no longer rents boats. I have been able to get 6 of them running perfectly with very little work. I am stuck on motor #7. I have rebuilt the carb and put new spark plugs in it. This one appears to have been run for only a short time, because it looks much less used than the rest. It will almost start every pull. I can hear fuel go into the carb when I push the prime button, so I know it is getting fuel. It doesn't seem to matter if I prime it or not, it almost starts everytime I pull it. My arm is getting tired. It has good compression on both cylinders at around 100 PSI. The spark looks a little weak to me, but I don't have a spark gap tester. I have spare motors, where should I start on this baby? What ignition component would you swap out first? Coil, switchbox. I would like to know which part is bad, so I can use the rest on another motor. Am I missing anything else? I am also looking for used cowlings for a couple of these motors if anyone knows where to find one. They seems to be in short supply.