Reply To: Impeller stops sucking at higher speed

[Don]

If the intake screen/plug are both OK, then I would suspect the sealing surface between the SS impeller plate and the gearcase housing. At slow speeds, the water level is high inside the gearcase, so there wouldn’t be much of an effect…But, once the boat speed increases, the water level inside the gearcase drops allowing air to be drawn in under the SS impeller plate…This is a weak link in many of the OMC gearcases due to aluminum corrosion/erosion in that area…. Oftentimes, guys break off the little impeller housing screws also, lousy repair jobs, or just leaving the broken screw there will lead to poor sealing also…