04 Mercury 150 saltwater rough mid throttle

I have an 04 Mercury 150 saltwater that runs a little rough mid-throttle. Runs ok at idle and wide open great, but lower to mid range kind of rough and tends to vibrate a little. Is this normal with this motor? I have read this motor loves wot, so not sure if it is just a characteristic of this motor of if it is something I need to check out.