50 hp runs rough

I have a 1998 50 hp 4stroke. It runs rough at idle almost like it vibrates till about 2500 rpm then it smooths out. I have changed the plugs, water separator, and put an external tank on it and had no change. It gets used at least once a week, so it has not sat for a long period of time. Any ideas what it could be. Thank you

[boats.net]

Probably needs carbs removed and cleaned.

Even though it gets used all the time you think the carbs could be gummed up or have trash in them?

Thanks guys for the advice i will give it a try.