After a run back to the landing of about ten to fifteen minutes at close to WOT my 150 Merc 4stroke is very difficult to shift. We noticed that the RPMs were running about 1400 which obviously is the reason why it won't shift. This is the third time i fished all day with no problems and when i got back to the landing after a longer than normal run, the problem occurs. Why is my throttle seemingly "stuck" at this higher than shifting range only after the longer runs? Serial No. of motor 2B245490.