motor will slip out of forward gear when i increase rpms. revrese gear slips but not all the way. the power head is a 62 and the lower leg is a 60. i have both parts catalog and the legs are the same as far as i can see. i have rebuilt carb, ignition, water pump. to get at the water pump the head had to be removed. could i have missed somthing reinstalling or do i have to look to the gear case? phil