We ran our boat 30 mins at 3200rpms, all gauges were fine the entire way to our stop. We slowed down to obey a wake zone and then started to run again at 4000rpm for 5 mins, all gauges were normal. Slowed down after those 5 mins to dock and lost the starboard engine. Engine would/will start hard but doesn’t sound like its hitting all cylinders. Any suggestions on where to start my diagnosis.

As with all engines:
Start with:
Scan for trouble codes
check/test ignition components (when you remove each plug get a good look for water/lean/rich/etc)
check fuel pressure
check compression all cylinders