Having problems with the motor getting on plane, once on plane it loses about 20 mph only running about 5200 ripms. Both while trying to get on plane and at top end the motor has a miss in it or cuts out as if it has water is in the fuel.It also has a rough idle to it and will die after a few seconds while in neutral. I have drained both tanks put a higher grade of gas in it and have checked all six coils with a spark tester which all show to have a spark. I have also changed the spark plugs and the water separator.What else could cause this issue?

Need to have your air and fuel pressures checked could have a weak air compressor these motors don't just rely on spark and your fuel. For a Optimax to run properly all three air fuel and spark need to be right. Air pressure should be 94+-2 psi and fuel should be 108+-2 psi. That's where I would start. If your not getting any warnings it is something that is not monitored by the ECM......OPTI

might need filters and air and fuel injectors clean