HI, I've got a Johnson 1984, 90hp V4, crossflow. 13 3/8 x 17prop. I just got it. The max rpms I am getting are 4000-4200(WOT). I thought that they like the high revs, 5500. I checked the spark plugs and line to the plugs there's spark. My last o/b died by rod through caseing. Also the tacho goes...