Disassemble marker and take a look at the bolt (the thing that the pump arm is screwed into). If you can see a hex key/screwdriver type end then you can probably tune the marker by turning it in away from where the paint sits to shoot higher. If you don't have one, then you need to get yourself a
set of springs to tune the marker to a higher velocity.
You could also make a spring, if you know what you're doing with spring wire... (you need a stiffer main spring for a higher velocity)