If you are happy with your current prop other than a sloppy hole shot, Adding ports (probably 3/8") under the leading edge of the blades (prop shop chore) will certainly help, or find a ported prop with the closest resemblance to your current prop and if you buy a Mercury prop you can get rubber plugs to change the diameter of the holes for specific tuning...to name one supplier.
If not happy then adding another blade will depend on the engines ability to drive it adequately and usually another blade is more lossy at high speeds as the efficiency is less than a 3 blade of the same basic design and pitch is usually dropped at least 1" to compensate for that loss.
