Yamaha 200 V Max Engine Miss Fire

Have a 200 V Max Yamaha outboard non HPDI. Have an engine miss fire. Has been into the shop and they say that it had bad O2 sensor gasket and they decarbonized the engine. The engine runs aprox the same and still has the miss fire that seems to even out at higher speeds, however it may still miss fire but covered by the higher rpms. Have also installed new spark plugs and fuel filter. Any ideas?
Thank you
nkelly57

[boats.net]

It's hard to say, the best way is to troubleshoot on water when the problem happens. Test ignition system, run fuel system checks and test o2 sensor. Did they do any test on the water when worked on o2.

Did no work on the water. Did check compression and is ok.