Engine is 50HP Mercury, 4-stroke, carbeurated, year 1999.<br />It will run okay up to about 3500 RPM. (This is about max displacement speed for the boat.) Upon applying more throttle the engine starts running rough and will get no more than 3800 rpm, no matter how much throttle. If I apply WOT from standing start it will start running rough earlier, but will still max at 3800 rpm. Max should be about 5000 rpm. Out of gear, it will run on up past 3800 with no problem. I did change plugs and fuel filter, but those were no help. Based upon other threads I've found here this sounds like carbeurator problem. Is that something I could try to fix myself? Are there other things I should check?<br /><br />I do have the service manual and in my younger years I repairs my vehicle engines, but I've never tinkered with outboards. Wouldn't mind giving it a try though.<br /><br />Chuck H.