After a few hours of problem free boating on the lake the fuel line on my Johnson 40VRO came loose from the motor and it shutdown. After a few minutes I was able to figure out the problem. After reconnecting the line and restarting the motor, it had only half its original power. On my way back to the launch it started firing on both cylinders again and ran great. I felt relieved. The next time I started the motor it had only half its power again. I have narrowed it down to the top cylinder not firing. I replaced both plugs with Champion Marine plugs. No change.
I swapped the coils and the problem is still in the top cylinder. I think that eliminates it being a coil. I can only achieve 1700 RPM at best.
What could possibly have caused this and how can I fix it????