Throttle Sticking on 150 Speedster

[mnewell]

Just bought a used 2007 150 Speedster 155hp. After boating a few hours running at high rpms I was unable to to throttle back below 6000. Quite disconcerting but fortunately out in open water and used the kill switch. moved the throttle back to idle position while shutoff then hit the start switch and away we go again at high rpms. Again hit the kill switch, after several iterations I decided to look at the throttle body on the engine. it appears that the cam would stick in a high fuel flow position, even when i moved the throttle control back towards idle it would only roll back a small amount. I searched on this forum and found the same issue on a 200 speedster but that problem was in the throttle control lever and not on the cam. i was able to rotate the cam manually until it would snap back to the idle position. I also found that moving the throttle control lever to full foward then snapping it back to idle a few times would help "unstick" the cam. the problem continued to occur numerous times, when i would go to a higher rpm setting the cam seemed to get stuck at the higher setting as i increased throttle. hoping this is not an expensive fix. any help would be appreciated.