Posted this in another area before I saw this one. I had a severe cavitation problem on takeoff and tight turns with my little 16' Glasspar delMar with a 65 hp Mercury. Running a 12.5" 16p prop with no cupping on the blades. Once it got rolling it would really dig in, but getting up there took a while and was like slipping the clutch on a manual shift car. I put on an original style Doel-Fin and I was amazed at the improvement. No more slipping on hole shots, and a lot better in tight turns at full throttle. Still working on finding the perfect prop for this rig, but for now the Doel-Fin has really upped my enjoyment of the boat.