My engine seems to run fine at slow speed, but on full open throttle it feels as thought the fuel is not getting through. It is a 40 2 stroke oil ing. 1990. It feels as though I am trying to get through a brick wall. I have relpalced the plugs and the fuel filter. When using the flush kit. The motor sounds good using the choke. But when in the water. At the throttle fully open it just wont go. Trying to go, but feels like I am being pushed back. New at this any help would be great.... Thanks