Ran the boat south on the bay today and it ran just fine. On the return trip we were only running about 3000 rpm because of rough water and once we got into calmer waters I tried to open it up but it would not run any fast than 4300 rpms/65 mph. I don't think I can find a scan tool before Tuesday so my question is. Does anyone have any suggestions on were to start?

I'd look to see all the spark plug wires are on securely,,sounds like its down a cylinder or 2.not sure the knock sensors will let it go up that high.I've had the knock sensors on my boat trip and limit rpm,but can't remember how high?if you can get to them easily,maybe disconnect for 1 blast(quickly) see if that lets it rev.then you'll have to find out why.
my case,rocker stud had been backing out till it finally went so far a push rod fell out of the cup.fixed it at the dock during a lunch stop.that was a *****.KE valve covers wouldn't come off betw gil mani and mpi runners.

I literally just came back inside from putting the boat back inside. I changed the fuel filters, checked the plugs for fouling, snugged up the wire connectors, checked the timing. Now I need some clear weather to run it. Hope it was something simple.