Missing at slow speed

[Hal380]

Just dropped my V20 in yesterday and while on a trial run noticed at low speed the engine sounds like it missing and there is some vibration. At higher speed it seems to even out. Any suggestions?

Things I already have done:
changed plugs
new fuel filter
fresh fuel with startron added
Fuel water separator installed.

I'm not much of a mechanic so I don't want to mess with this thing too much. May have to get a mechanic on the water to actually see what's happening.

Any help would be appreciated

Regards

Hal