I have a 79 Hunter 30. I was getting about 5.5 max. Had a diver clean the bottom and the prop. At 2200 rpm speed went from 4.5 to 5.6. Got 6kts under power easily. Got 6.6 SOG close hauled in about 13kts of wind. Had a little current helping, but she was flying! TO keep things clean get a wide hard bristle broom and an extendable painter's handle (6' - 12'). Put a bend in the extended part about 12" from the end (best to use a tubing bender) so you can "sweep" the hull, keel & rudder once a month or so. This is all for salt water of course.